The Diabetic Foot Ulcer Scale (DFS): a quality of life instrument for use in clinical trials

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1 The Diabetic Foot Ulcer Scale (DFS): a quality of life instrument for use in clinical trials Linda Abetz*, Monica Sutton, Lesley Brady, Pauline McNulty, Dennis D. Gagnon ABSTRACT The diabetic foot ulcer scale (DFS) questionnaire is a specific instrument designed to assess the impact of foot ulcers and their treatment on quality of life in people with diabetes. Based on the results of semi-structured interviews and focus-group discussions with foot ulcer patients and caregivers, the DFS consists of 58 items grouped into 11 domains: leisure, physical health, daily activities, emotions, noncompliance, family, friends, positive attitude, treatment, satisfaction, and financial. Two studies have been conducted to develop and validate the DFS. The first of these included 173 patients with diabetes and current foot ulcers (n = 48), healed foot ulcers (n = 54), or no history of foot ulcers (n = 71). A generic measure of health status, the SF-36, was used to test construct validity. The DFS had good internal consistency. Significant differences between patients with current ulcers and those with healed ulcers were observed in the mean scores for the leisure, emotions, and financial domains (p < 0.05). Marked differences were also observed in physical health, daily activities, and friends domains, indicating that the DFS is able to discriminate patients with healed ulcers from those with current ulcers. The DFS was further evaluated in a relevant clinical setting (n = 288); confirmatory factor analysis confirmed the hypothesised factor structure of the DFS, but with slight suggestions for improved scaling. The DFS scales also demonstrated adequate test retest reliability and sensitivity to change in wound status over time, indicating its appropriateness for use in clinical trials. Copywrite 2002 John Wiley & Sons, Ltd Practical Diabetes Int 2002: 19(6); KEYWORDS diabetes; foot ulcer; quality of life; treatment; diabetic foot ulcer scale Introduction Neuropathic ulcers of the lower extremity are a common and potentially serious complication of diabetes. Each year, 2.5% of people with diabetes develop foot ulcers, while 15% of all patients with diabetes will develop chronic ulcers on the foot or lower extremity during their lifetime. 1 3 These diabetic foot ulcers are associated with increased morbidity and mortality rates. For example, the annual amputation rate Linda Abetz, BA, MAPI Values Ltd., Cheshire, UK; Monica Sutton, SRN, RSCN, Lesley Brady, SRN, Royal Hallamshire Hospital, Sheffield, UK; Pauline McNulty, PhD, Dennis D. Gagnon, MA, MABE, R.W. Johnson Research & Development LLC. *Correspondence to: Linda Abetz, MAPI Values Ltd., Adelphi Mill, Grimshaw Lane, Bollington, Cheshire, UK, SK10 5JB Received 23 October 2001 Accepted in revised form 11 April 2002 for people with diabetes is 15 times higher than the amputation rate for nondiabetic individuals, 4,5 and less than 40% of those individuals with diabetes will survive for 5 years or longer following a lower extremity amputation. 5 In a study of 6000 patients with diabetes in the United Kingdom, 2% were found to have active foot ulcers and 2.5% had undergone an amputation. 6 In healthy individuals, most foot lesions will eventually resolve with proper wound care. In individuals with diabetes, however, the aetiology of foot ulcers is multifactorial, 2,7 and the healing process can last several months, even in the absence of complications. The prolonged healing time and complex treatment, which requires adherence to a nonweight-bearing regimen, can represent a significant burden to patients and their families. Lack of compliance with a nonweight-bearing regimen is a problem in a proportion of patients, and ulcer recurrence rates are high (35% after 3 years; 70% after 5 years). 8 Along with increased morbidity, foot ulcers can lead to lifelong disability and may substantially diminish the quality of life for these patients. 9 Specifically, patients with diabetic foot ulcers have restrictions on mobility, 10 poor psychosocial adjustment, 11 and lower self-perceptions of health than patients who do not have ulcers. 12 To date, however, no specific quality-of-life instrument has been developed for use in the care and management of nonhealing diabetic foot ulcers. An understanding of the specific effects of chronic diabetic foot ulcers on individual patients quality of life is central to the direction of treatment, management of compliance, and patient/practitioner communication. The objective of this study was to develop a specific instrument to measure the impact of diabetic foot ulcers on the quality of life of patients. This instrument was developed for use in clinical trials to assess the benefit of treatments that promote ulcer healing. Methods Item/scale identification The quality of life concepts relative to foot ulcers were initially identified in a pilot Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd. 167

2 study conducted in the United Kingdom that involved face-to-face semi-structured interviews with ten patients (six men, four women; mean age, 61 years; range, 46 to 74 years) and three caregivers. All of these patients currently had diabetic foot ulcers, and were referred by either a neuropathy specialist/consultant or a diabetic foot ulcer nurse. Subsequent focus-group discussions with patients and caregivers were conducted to define further the domains of quality of life affected by diabetic foot ulcers. A total of 14 patients and 11 caregivers from the United Kingdom consented to participate in these discussions, consisting of two patient groups and two caregiver groups. The groups were not attended by anyone involved in treating the patients and were all facilitated by the same moderator. Following each focusgroup discussion, the research team reviewed the group responses to identify major issues. Themes arising in one group were presented to subsequent groups for further elucidation of the concepts and domains. These themes included the impact of ulcers on mobility and the resulting implications for daily activities and social activities, the impact of ulcers on leisure activities, and psychological issues, such as knowing that one is at high risk for ulceration, discovering the presence of an ulcer, having to obtain treatment for foot ulcers, or having a toe, foot, or leg amputated. The verbatim descriptions elicited from patients and caregivers during the discussions were used to generate a comprehensive list of items according to the following criteria: (i) a time reference was established; (ii) items were grouped into domains; and (iii) proposed response choices were considered. This was accomplished by extracting quotes from patient interview transcripts, and using these quotes to determine how patients describe their condition in lay terms. The comments were then categorised into domains, and the instrument was developed according to standard criteria, which includes the absence of value-laden words, bias, or jargon, as well as the absence of double inquiry within a single item. Other criteria considered when generating items were grammatical correctness, appropriateness of the recall period for the concept being measured, comprehensiveness, relevance, and clarity of wording. The items generated using these criteria were constructed into two preliminary test questionnaires, one for patients and one for caregivers. The subsequent validity testing was conducted for the patient questionnaire only. The face and content validity of the test questionnaire were evaluated during faceto-face interviews with 12 newly enrolled patients (eight men, four women) at a local foot clinic. After patients completed the questionnaires, they were asked by the interviewer to evaluate each item according to clarity and ease of comprehension on first reading; relevance; absence of ambiguity; absence of technical terms (medical jargon); absence of double inquiry in the same question; absence of value-laden words. Cross-sectional validity The validity of the Diabetic Foot Ulcer Scale (DFS) was initially assessed in a cross-sectional study conducted in three diabetic foot centres in the United Kingdom. A subsequent longitudinal study assessed the test retest reliability and the sensitivity to change in wound status for this questionnaire. The objective of the cross-sectional study was to assess the measurement properties of the questionnaire, including the scaling assumptions, internal consistency reliability, and construct validity. Discriminant validity was examined against predefined hypotheses about the clinical severity of the ulcers, and healed versus nonhealed status. The cross-sectional study included adult patients ( 18 years of age) with type 1 or 2 diabetes and good diabetic control as well as a neuropathic or mixed neuropathic/ischaemic foot ulcer. Target (primary) ulcer size was limited to cm 2, and patients could have up to two satellite (secondary) ulcers. Patients with more than three ulcers, or ulcers resulting from any cause other than diabetes, were excluded. Patients with connective tissue or ischaemic disease, or chronic alcohol or drug abuse, were also excluded. The cross-sectional study also included a sample of adults ( 18 years of age) with diabetes, matched for age, sex, and type of diabetes, and a history of ulcers that had healed within the three previous months, but with no current foot ulcer. This group was used as a comparative cohort, and exclusion criteria were identical to those of patients with current lower extremity ulcers. A similarly matched group of patients with diabetes but with no history of neuropathy or lower extremity ulcers was also included in the cross-sectional study to help discriminate between those effects that are specifically related to foot ulcers and those related to diabetes in general. All patients gave written informed consent before participation in the study, and ethics committee approval was obtained. The DFS was administered together with the SF-36, which was selected as the gold standard reference because of its well documented validity. The incorporation of the SF-36 allowed for an assessment of the relative burden of foot ulcers and aided in the interpretation of the DFS results. Study investigators also recorded patient demographics and relevant medical details, including duration of diabetes, foot ulcer history, control of diabetes (HbA 1c ), and foot ulcer severity according to clinical criteria. Patients were asked to complete the pen and paper version of the questionnaire when they came for routine ulcer assessments. To ensure that patients fully understood how to complete the questionnaire, investigators explained the procedure by reading the instructions provided to the investigator. Beyond that, investigators were instructed not to help patients interpret or answer any questions. The data were entered using a double-entry validation technique and were analysed using Statistical Analysis System (SAS, SAS Institute Inc., Cary, NC). Initial psychometric analyses for the DFS were performed in the cross-sectional study on the population of patients with current ulcers. DFS scores were based on the sum of all items associated with that domain. Where necessary, raw item scores were reverse coded so that the minimum possible score (1) represented the worst quality of life, and the maximum possible score (5) represented the best quality of life. All of the DFS scales were scored from 0 to 100, with higher scores indicating better quality of life. DFS scale scores were calculated when less than 50% of the items for that scale were missing. The initial scales were established using the content of each item, and were based on the patient discussions. Scaling assumptions were tested using the content of each item and Varimax analysis. These scaling assumptions were further examined using a multitrait analysis program (MAP) to determine whether individual items could be grouped into a more limited set of scales. The MAP analysis is based upon a review of item scale correlations that indicate the degree to which each scale measures a single concept (item-convergent validity) and different scales measure separate concepts (item-discriminant validity). The internal consistency reliability of each 168 Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd.

3 Table 1. Content of the Diabetic Foot Ulcer Scale (DFS): Domains and Items Domain: Leisure (Five items scaled as 1 = not all, 2 = a little bit, 3 = moderately, 4 = quite a bit, and 5 = a great deal) How much have your foot ulcer problems: 1a) Stopped you from doing the hobbies and recreational activities that you enjoy? 1b) Changed the kinds of hobbies and recreational activities that you enjoy? 1c) Stopped you from getting away for a holiday or weekend break? 1d) Made you choose a different kind of holiday or short break than you would have preferred? 1e) Meant that you had to spend more time planning and organising for leisure activities? Domain: Physical health (Six items scaled as 1 = none of the time, 2 = a little bit of the time, 3 = some of the time, 4 = most of the time, and 5 = all of the time) Because of your foot problems, how often have you felt: 2a) Fatigued or tired? 2b) Drained? 2c) That you had difficulty sleeping? 2d) Pain while walking or standing? 2e) Pain during the night? 2f) Unwell because of taking antibiotics or other medicine for infection? Domain: Daily activities (Six items scaled as 1 = none of the time, 2 = a little bit of the time, 3 = some of the time, 4 = most of the time, and 5 = all of the time) Because of your foot problems, how often have you: 3a) Had to depend on others to help you look after yourself? 3b) Had to depend on others to do household chores such as cooking, cleaning, or laundry? 3c) Had to depend on others to get out of the house? 3d) Had to spend more time planning or organising your daily life? 3e) Felt that doing anything took longer than you would have liked? 3f) Felt restricted in your daily life? Domain: Emotions (17 items scaled as 1 = not at all, 2 = slightly, 3 = moderately, 4 = quite a bit, and 5 = extremely) Because of your foot problems, have you felt: 4a) Angry because you were not able to do what you wanted to do? 4b) Frustrated by others doing things for you when you would rather do them yourself? 4c) Frustrated because you were not able to do what you wanted to do? 4d) Helpless to cure your ulcer(s)? 4e) Worried that your ulcer(s) will never heal? 4f) Worried that you may have to have an amputation? 4g) Worried about injury to your feet? 4h) Depressed because you were not able to do what you wanted to do? 4i) Worried about getting ulcers in the future? 4j) Worried about being a burden on others? 4k) That you have no control over your life? 4l) Angry that this has happened to you? 4m) Alone? 4n) Frustrated because you have difficulty in getting about? 4o) Frightened about the future? 4p) Badly about yourself because you can no longer work or be productive? 4q) Hopeless; that things will never get better? Domain: Noncompliance (Two items scaled as 1 = none of the time, 2 = a little bit of the time, 3 = some of the time, 4 = most of the time, and 5 = all of the time) Because of your foot problems, how often: 5a) Have you done things that you knew were not good for you such as eating, drinking, or smoking too much? 5b) Did you disregard medical advice about how to care for your ulcer? Domain: Family (Five items scaled as 1 = not applicable/no spouse/no family, 2 = none/not at all, 3 = a little bit, 4 = quite a bit, and 5 = a great deal) Because of your foot ulcer problems, how much: 6a) Strain has there been on your relationship with your spouse or partner? 6b) Strain has there been on your relationship with other family members? 6c) Do you argue with your spouse or partner? 6d) Have you felt that you are a burden on your family? 6e) Have you felt that there has been a decline in your sexual relations? Domain: Friends (Five items scaled as 1 = not at all, 2 = a little bit, 3 = moderately, 4 = quite a bit, and 5 = a great deal) Because of your foot ulcer problems, how much have you felt: 7a) Guilty because your friends have to change plans to fit in with your limitations? 7b) That your circle of friends is getting smaller? 7c) That there are restrictions on the kinds of things you do with your friends? 7d) Hindered in your social life? 7e) That you are a burden on your friends? Domain: Treatment (Four items scaled as 1 = not at all, 2 = a little bit, moderately, 4 = quite a bit, and 5 = extremely) Because of your foot ulcer problems, how much are you bothered by: 8a) Having to keep the weight off your foot ulcer? 8b) The amount of time involved in caring for your foot ulcer (including dressing changes, waiting for the district nurse, and keeping the ulcer clean)? 8c) The appearance, odour, or leaking of your ulcer? 8d) Having to depend on others to help you care for your foot ulcer? Domain: Satisfaction (One item scaled as 1 = not at all, 2 = a little bit, 3 = moderately, 4 = quite a bit, and 5 = extremely) 9) How satisfied have you been with your medical care for your foot ulcer problems?* Domain: Positive attitude (Five items scaled as 1 = not at all, 2 = a little bit, 3 = moderately, 4 = quite a bit, and 5 = a great deal) Because of your foot ulcer problems: 10a) Have you been taking better care of your feet?* 10b) Have you been taking better care of yourself in general?* 10c) Have you felt closer to a spouse or a partner?* 10d) Have you a greater appreciation of your friends?* 10e) Have you felt happier?* Domain: Financial (Two items, each scaled differently; see below) Because of your foot ulcer problems: How much money have you spent out of your own pocket on other things such as shoes, taxis, higher phone bills, and home modification? (Scaled as 1 = none, 2 = a little bit, 3 = some, 4 = quite a bit, and 5 = a great deal) How bothered have you been by the money you have spent out of your own pocket on things such as shoes, taxis, higher phone bills, and home modification? (Scaled as 1 = not at all, 2 = a little bit, 3 = moderately, 4 = quite a bit, and 5 = extremely) *These items not reverse coded before summation of domains. The Diabetic Foot Ulcer Scale has been reproduced with the kind permission of Johnson & Johnson Research & Development, LCC Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd. 169

4 Table 2. DFS Item Groupings Used in the Longitudinal Study Domain Item number(s) Leisure 1a e Physical health 2a e Medicine effect 2f Daily life 3d f Dependence 3a c, 8d Emotions 4a q Healthy behaviours 5a Medical compliance 5b Family life 6a e Friends 7a e Ulcer care 8a c Satisfaction 9 Personal care 10a, b Positive relationship 10c, d Financial burden 11, 12 scale was measured using Cronbach s alpha coefficient. A Cronbach s alpha coefficient value of greater than 0.70 was considered acceptable for the use of multi-item scales in conducting comparisons between groups. 13 Construct validity for each item was supported if the specific scale measuring a concept was substantially correlated (>0.4) with the SF-36 scale measuring the same concept. The SF-36 was chosen as the gold standard because it has been used successfully to distinguish among patients with varying degrees of diabetes severity, and between patients with or without complications of diabetes. Although a diabetes-specific instrument could have been used as a standard, none of the validated instruments available at the time of the study were considered appropriate (i.e. they related more to diabetes symptoms than to quality of life or health status). Validity was further examined by postulating that quality of life scores would be higher in patients with healed ulcers than in patients with current ulcers (known groups validity). The ability to distinguish between patients with healed versus nonhealed ulcers and between different clinical severity of foot ulcers, based on quality of life scores, was examined using analysis of variance (ANOVA) and appropriate correlations. Sensitivity to clinical change Further validation of the DFS took place in a prospective, randomised, doubleblind, placebo-controlled trial testing the efficacy and safety of recombinant human-plateletderived growth factor-bb (rhpdgf-bb; becaplermin) for the treatment of chronic diabetic foot ulcers in 326 subjects that was conducted at approximately 40 centres in the United States and Europe. Inclusion in this 20 week study required the presence of at least one chronic, full thickness lower extremity diabetic ulcer and possibly up to two additional satellite ulcers. Patients were administered both the SF-36 and the DFS instruments at four time points throughout the study: the screening visit; study completion (ie, after 20 weeks of study duration, or at the time of complete ulcer healing or early discontinuation whichever occurred first); and 4 and 12 weeks after study completion. Beyond collecting DFS data in the UK and the US in this prospective trial, subjects at selected sites in Belgium, Denmark, France, Italy and the Netherlands were administered the DFS. Translations of the DFS for these non- English-speaking countries adhered to rigorous procedures developed to yield psychometrically valid versions of quality of life instruments, incorporating both forward and backward translations as well as patient cognitive debriefing. Based on an analysis of preliminary, blinded data of the performance of the DFS in a similar patient population, the questionnaire used in this study was modified slightly from the initial version, in that some items were found to fit better in other domains. For example, the daily activities scale from the cross-sectional study was further divided into two subscales: daily life (which included items d f from the original DFS questionnaire; see Table 1) and dependence (which included daily activities items a c, plus item d from the treatment subscale). The two-item noncompliance scale was divided into the healthy behaviours (item a) and medical compliance (item b) subscales. The positive attitude scale was divided into the personal care (items a and b) and positive relationship (items c and d) scales; item e was dropped from the questionnaire. Finally, item d of the ulcer care scale was shifted to the dependence scale. A summary of the item groupings into scales is presented in Table 2. A confirmatory factor analysis of the DFS was conducted in an effort to verify the appropriateness of the DFS scaling used in the prospective, longitudinal study. Factor loadings were derived, indicating how much better the model would fit the data if a constrained item were freed to associate with some other domain. The DFS was evaluated for sensitivity to change in wound status using the mixed-modeling methods of Laird and Ware for efficient use of the repeated measurements. 14 The model contained the following covariates: target ulcer healing, timing of visit (i.e. four weeks and 12 weeks after study completion), gender, presence of more than 1 ulcer at baseline, age at baseline, and baseline ulcer area. The SAS MIXED Procedure (SAS Institute, Cary, NC) was used to analyse each of the subscales. Finally, the test retest reliability of the DFS was examined using a lower bound estimate that was obtained by computing correlations between subscale scores obtained at screening and at study completion for patients treated with placebo. It should be noted that these results are considered preliminary because the analysis was conducted in placebotreated patients whose clinical condition may have improved or deteriorated over the course of the 20 week study. For research purposes, a test retest reliability of 0.70 is generally considered acceptable. Results Item/scale identification Patient sociodemographic and clinical characteristics are shown in Table 3. With the exception of age, the study groups were well balanced. Mean age was significantly higher in patients with healed ulcers compared with that of patients with no history of ulcers (p < 0.05). The loss of mobility caused by the nonweight-bearing treatment regimen was a major factor contributing to the effects on quality of life described by patients in a wide range of domains, including restrictions in daily activities, leisure and social interaction, strain on relationships, and feeling a burden. Patients experienced a substantial amount of frustration and anger because of these restrictions. The uncertainty as to whether or when the ulcer would heal was also a source of worry to patients. The domains that emerged together with their definitions are summarised in Table 1. The new questionnaire resulting from this phase of the study was named the Diabetic Foot Ulcer Scale (DFS); a full report of the findings from the patient and caregiver discussions can be found in the study by Brod Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd.

5 Cross-sectional validation Psychometric results for scaling assumptions are summarised in Table 4. For convergent validity (i.e. an item s correlation with its own scale), 93% of items met or exceeded the standard criterion (r 0.4). Table 3. Sociodemographic and Clinical Characteristics. Current ulcer Healed ulcer No ulcer history (n = 48) (n = 54) (n = 71) Mean age, years (SD) 58 (11.23) 65* (11.92) 55 (14.82) Sex, % Male Female Marital status, % Married Living with partner Employment, % Full time Retired Education, % Primary Secondary Tertiary Duration of diabetes, years (SD) 17 (11.34) 18 (12.10) 12 (9.22) Treatment, % Insulin Drugs Diet HbA1c, % (SD) 8.49 (2.76) 8.52 (2.83) 9.53 (1.82) Number of hypoglycaemic episodes in previous month (SD) 0.95 (2.39) 0.31 (0.78) 1.15 (0.39) Number of diabetes-related diseases Number of diseases not related to diabetes (SD) 0.65 (0.86) 0.43 (0.74) 0.42 (0.66) * p < 0.05 versus patients with no ulcer history. Four items did not meet this criterion: two items in the noncompliance scale and one item each in the physical health and positive attitude scales. The noncompliance scale was heterogeneous by design in that it contained questions about compliance with foot care as well as compliance general to risk behaviours (smoking etc). The physical health item contained a general concept of feeling unwell in relation to treatment, as opposed to other items in the scale, which focus on the disease itself and on specific areas of physical health (fatigue, sleeping, pain). Finally, the positive attitude question Because of your foot ulcer problems have you felt happier? did not fit well partly because of a high floor effect, with little or no endorsement of patients feeling happier because of their foot problems. Item-discriminant validity (i.e. an item has a higher correlation with its own scale than with other scales measuring other concepts) with respect to scaling successes ranged from 65% (noncompliance) to 100% (leisure, positive attitude, financial). With the exception of the noncompliance scale, all scales met or exceeded acceptable levels of item discriminant validity ( 85%). Of note, the physical health scale just met the criterion at 85%. More than 85% of items met the standard criterion for homogeneity (i.e. mean item scale correlation > 0.30). Again, the noncompliance scale performed worst (mean item scale correlation = 0.12). The positive attitude and physical health scales just met the criteria at 0.30 and 0.33, respectively. Finally, for reliability at the scale level (Cronbach s alpha) all but two scales met the minimum standard criterion of Noncompliance and positive attitude indicated reliability coefficients < Correlation of DFS domains with the SF-36 indicated good construct validity in leisure, physical health, and daily activities Table 4. DFS Scaling Success and Reliability Item convergent Item discriminant Internal validity validity consistency reliability Domain Number of Mean item scale Cronbach s items (% 0.40) Scaling success (%) correlation alpha Leisure Physical health Daily activities Emotions Noncompliance Family Friends Treatment Satisfaction 1 Positive attitude Financial Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd. 171

6 Table 5. Correlations of SF-36 and DFS subscales: Pearson correlation coefficients (All p-values significant except where noted). SF-36 scales DFS scales Physical Role Bodily General Social Role Mental function physical pain health Vitality function emotional health Leisure * * 0.22* Physical health Daily activities Emotions Noncompliance 0.04* 0.02* 0.04* 0.06* * 0.01* 0.06* Friends * * Treatment * 0.26* Positive attitude 0.10* 0.21* 0.11* 0.17* 0.04* 0.01* 0.22* 0.17* Financial * * * p value not significant. scales (Table 5). These domains were better correlated with the physical health scales of the SF-36 and less correlated with the mental health scales. The emotions scale of the DFS was significantly correlated with all SF-36 scales, but was most highly correlated with the SF-36 social functioning scale (r 0.64, p < ) and least correlated with the SF-36 bodily pain scale. Whilst the emotions scale was not as highly correlated with the SF-36 mental health scale as one might expect, it is noteworthy that, when comparing the SF-36 mental health scale to all the DFS scales, the SF-36 mental health scale was most highly correlated with the emotions scale (r = 0.51). This finding was not surprising, given that the items in the emotional scale are directly related to patients worry and frustration about their physical wellbeing and about becoming a burden to others. The scaling of the DFS based on initial assumptions was satisfactory. Some item reduction and rescaling, however, could be performed. In particular, the emotions scale should probably be divided into subscales or renamed as a worry and frustration scale. Additionally, the Are you happier because of your foot ulcer? item from the positive attitude scale should probably be dropped. Likewise, the two items in the noncompliance scale should most likely be considered as categorical variables, given their heterogenous nature (compliance with treatment versus risk behaviours). However, no item reduction was performed in this analysis because of the small sample size. To verify the representative nature of the patient sample used for the cross-sectional validation analysis, mean SF-36 scores for patients with diabetes and no Figure 1. Mean scores obtained on the SF-36 for the study population comprising patients with diabetes and with no history of foot ulcers, and normative data from the United States and the United Kingdom. 15 history of foot ulcers were compared with scores for patients with diabetes from the general population in the United States and the United Kingdom. 15 The scores indicated that the health status of the study population was consistent with other groups of patients with diabetes (Figure 1). Figure 2 compares the mean SF-36 scores for the three study groups. The generally lower scores in patients with current ulcers and patients with healed ulcers, compared with those with no history of ulcers, support the concept that patients with lower extremity diabetic ulcers have a poorer quality of life than people with diabetes with no history of foot ulcers. The patients with no history of foot ulcers scored significantly higher on the physical functioning and role physical domains (p < 0.05). The healed ulcer group had significantly higher scores than the current ulcer group for physical functioning and role physical domains (p < 0.05). For bodily pain, the scores of patients with healed ulcers were significantly higher than those of patients with current ulcers and equal to those of patients with no history of foot ulcers. In testing the known-groups validity of the DFS, differences were seen between patients with healed ulcers and patients with current ulcers in a number of domains (Figure 3). Patients with healed ulcers generally had a better quality-of-life profile than patients with current ulcers. There were significant differences in the leisure, emotion, and financial domains between patients with healed ulcers and patients with current ulcers (p < 0.05). 172 Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd.

7 Sensitivity to clinical change Factor loadings derived from the DFS scaling used in the longitudinal study were generally good, with the exception that factor loadings for items 4f and, 6c e indicate that these items were not strongly related to their hypothesised domains. Modification indices suggest that the model would fit the data much better if item 8d were scaled with ulcer care rather than dependence. Additionally, modification indices suggest that allowing item 6d to associate with dependence rather than family life would also result in a better fitting model. Finally, allowing item 4b to be scaled with the dependence domain rather than with emotions would further enhance the fit of the model. Generally, the scaling of the items that were most sensitive to changes in wound status remained relatively constant in both versions of the questionnaire; as noted previously, a summary of the item groupings into the scales used for the longitudinal study is presented in Table 2. Patients with healed ulcers had significantly higher scores on leisure, medicine effect, daily life, emotions, and medical behaviours after adjustment for all other variables in the model (Table 6). Based on this sample, effective treatment for diabetic foot ulcers would be expected to have a positive impact on these quality of life domains during the 12 weeks following Figure 2. Mean (± SEM) scores obtained on the SF-36 for patients with current foot ulcers (n = 48), patients with healed foot ulcers (n = 54), and patients with no history of foot ulcers (n = 71). Figure 3. Mean (± SEM) scores obtained on the DFS for patients with current foot ulcers (n = 48) and patients with healed foot ulcers (n = 54). treatment. Of note, patients with larger ulcers at baseline had lower scores on leisure, daily life, dependence and family life subscales, but higher scores on the positive relationship scale. The test retest reliability analysis showed that five of the DFS subscales remained relatively stable over time in patients treated with placebo (physical health, dependence, emotions, family life, and friends), with correlation values >0.70 (Table 7). In contrast, four of the subscales (medical compliance, satisfaction, medicine effect, and personal care) had correlation values < 0.40, indicating that these scales tend to be less stable over time. The majority of the SF-36 scales demonstrated acceptable test retest reliability; however, the physical functioning, general health, and vitality subscales and the physical and mental component summary scales failed to meet this criterion. Overall, the correlations between pre- and post-treatment SF-36 scores were much lower than the reliability estimates reported in the SF-36 manual. 12 The low test-retest reliabilities of these items may be explained by the fact that some of these scales (for the DFS) consist of only one or two items; scales with very few items generally have lower test retest reliability than scales composed of more items. Additionally, the time between test and retest is rather long for testing reliability: up to 20 weeks in some cases. Change can be expected over the 20 week period, even though only placebo patients were included in the test retest analysis. Given this design, even the SF-36 correlations underestimate the test retest reliability of these scales. Thus, it is likely that the parallel DFS correlations also greatly underestimate the test retest reliability of the DFS subscales. Discussion Through discussion with patients, it was possible to identify quality-of-life concepts specific to foot ulcers and their treatment in people with diabetes. The questionnaire developed from these concepts is acceptable to patients, shows face and content validity, and measures the following domains: leisure, physical health, daily activities, emotions, noncompliance, family, friends, treatment, satisfaction, positive attitude, and financial. The DFS demonstrates good scaling properties in general, and has good reliability and validity. Moreover, the DFS shows good construct validity vis-à-vis the Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd. 173

8 Table 6. Parameter estimates for wound status in repeated measurements model*. Parameter Standard DFS Subscale n estimate error F-value p-value Leisure Physical health Medicine effect Daily life Dependence Emotions Medical behaviours Medical compliance Family life Friends Ulcer care Satisfaction Personal care Positive relationship Financial burden * Based on a mixed-effects repeated measurements model with the following factors: wound status, time, gender, presence of more than one ulcer at abseline, age, baseline ulcer area. Table 7. Test retest reliability of the DFS: correlations between quality of life subscale scores obtained at baseline and study completion. Subscales r-coefficient DFS Leisure 0.66 Physical health 0.72 Medicine effect 0.35 Daily life 0.68 Dependence 0.84 Emotions 0.82 Healthy behaviours 0.57 Medical compliance 0.00 Family life 0.70 Friends 0.77 Ulcer care 0.65 Satisfaction 0.16 Personal care 0.35 Positive relationship 0.59 Financial burden 0.62 SF-36 Physical functioning 0.50 Role physical 0.75 Bodily pain 0.81 General health 0.35 Vitality 0.67 Social functioning 0.74 Role emotional 0.78 Mental health 0.49 SF-36. The DFS was able to discriminate between patients with healed ulcers and patients with current ulcers for the leisure, emotions, and financial domains. The physical health, daily activities, and friends domains appeared to indicate substantial differences between patients with healed ulcers and those with current ulcers; however, these effects did not reach statistical significance. These results indicate that foot ulcers have a significant negative effect on the physical components of quality of life and often result in frustration due to limitations and worry about the future. These effects are reflected in the significantly lower scores obtained on the emotions scale for individuals with current ulcers compared with scores for individuals with healed ulcers. Importantly, while the SF-36 mental health scale was most highly correlated with the DFS emotions scale, the DFS emotional scale was most highly correlated with SF-36 social functioning and physical functioning scales than the mental health scale. This might be expected because the DFS emotions scale incorporates concepts of frustration due to the physical constraints imposed by the ulcer, worry about the future course of the ulcer, and the impact of the ulcer on family and friends. The sensitivity of the DFS to change in wound status over time has been demonstrated preliminarily in a prospective, multinational clinical trial of ulcer healing. Results of this study generally confirmed the construct validity of the DFS. Confirmatory factor analysis indicated that some of the items are closely related to more than one scale. A more stable, appropriate factor structure may be achieved with only minor rescaling of the current DFS. Thus, the next logical step in the development of the DFS would be to consider the results of the confirmatory factor analysis within the context of theoretically sound scaling changes. Additional confirmatory factor analysis should then be performed using an independent dataset to ensure the appropriateness and fit of the revised scales. In conclusion, the DFS can discriminate between patients with diabetes with healed ulcers and nonhealed ulcers, is sensitive to changes in wound status, and is therefore appropriate for use in clinical trials of patients with foot ulcers. Of note, the DFS is a measure specific to foot ulcers and not generic to diabetes. Finally, further analysis and research are warranted to optimise the subscale structure of the DFS. Acknowledgements We thank the nursing staff of Heartlands Hospital, Birmingham, the Manchester Diabetes Centre, and Salford Royal Hospital, who helped in the recruitment and briefing of patients for this project. Key points The diabetic foot ulcer scale (DFS) questionnaire is a quality of life instrument designed specifically to assess the impact of foot ulcers and their treatment on quality of life in people with diabetes, and has been validated in cross-sectional and longitudinal studies. Of note, the DFS is an instrument specific to foot ulcers, and not to diabetes. The DFS can discriminate between patients with diabetes with healed ulcers and current ulcers, is sensitive to changes in wound status, and is therefore appropriate for use in clinical trials of patients with diabetic foot ulcers. Additional analysis and research are warranted to further optimise the subscale structure of the DFS. 174 Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd.

9 We extend a special thanks to all of the patients, without whom the study would not have been possible, and we wish to acknowledge our colleague, Clare McGrath, formerly of MAPI Values, who directed the focus groups and cross-sectional study in the United Kingdom. Finally, we wish to acknowledge the invaluable editorial assistance of Erica Wehner, RPh. References 1. Palumbo PJ, Melton LJ, III. Peripheral vascular disease and diabetes. In: Diabetes in America, Harris MI, Hamman RF (eds). Washington, DC: US Government Printing Office, 1985,; Reiber GE. The epidemiology of diabetic foot problems. Diabet Med 1996; 13: S6 S US Dept of Health EaW. Report of the National Commission on Diabetes. Washington, DC: Government Printing Office, Most RS, Sinnock P. The epidemiology of lower extremity amputation in diabetic individuals. Diabetes Care 1983; 6: Reiber GE, Boyko EJ, Smith DG. Lower extremity foot ulcers and amputations in diabetes. In: Harris MI, Cowie CC, Reiber G, Boyko E, Stern M, Bennett P, eds. Diabetes in America. Washington, DC: U.S. Government Printing Office 1995, Young MJ, Boulton AJM, Macleod AF, Williams DRR, Sonksen PH. A multicentre study of the prevalence of diabetic peripheral neuropathy in the United Kingdom hospital clinic population. Diabetologia 1993; 36: Bild DE, Selby JV, Sinnock P, Browner WS, Braveman P, Showstack JA. Lower-extremity amputation in people with diabetes. Epidemiology and prevention. Diabetes Care 1989; 12: Walsh CH. A healed ulcer: what now? Diabet Med 1996; 13: S58-S60 9. Brod M. Quality of life issues in patients with diabetes and lower extremity ulcers: patients and caregivers. Qual Life Res 1998; 7: Walshe C. Living with a venous leg ulcer: a descriptive study of patients experiences. J Adv Nurs 1995; 22: Carrington AL, Mawdsley SK, Morley M, Kincey J, Boulton AJ. Psychological status of diabetic people with or without lower limb disability. Diabetes Res Clin Pract 1996; 32: Wikblad K, Smide B, Bergstrom A, Kessi J, Mugusi F. Outcome of clinical foot examination in relation to self-perceived health and glycaemic control in a group of urban Tanzanian diabetic patients. Diabetes Res Clin Pract 1997; 37: Nunnally JC. Psychometric Theory, 2nd edn. New York: McGraw-Hill Laird NM, Ware JH. Random-effects models for longitudinal data. Biometrics 1982; 38: McColl E, Steen IN, Meadows KA, et al. Developing outcome measures for ambulatory care an application to asthma and diabetes. Soc Sci Med 1995; 41: RCN Diabetes Nursing Forum News The Royal College of Nursing Forum represents nursing on a number of national groups and committees as well as within the RCN The committee has not met since I last reported for this column, but members have all been busy working on various projects, communicating with each other and with other organisations by . I will briefly update you here with three of these. Supplementary prescribing consultation Philippa Jones, our prescribing lead, has co-ordinated the Forum s response to the Department of Health s consultation on supplementary prescribing by nurses and pharmacists. If the proposals are approved, eligible nurses will receive training to become supplementary prescribers, and would be entitled to prescribe drugs and treatments for named patients with specific conditions, including diabetes, according to a clinical management plan (a protocol by another name) that has been agreed with a doctor for an individual patient. While we welcome the proposals, which would legalise some current practices, we have also pointed out that supplementary prescribing fails to recognise that, in many cases, the specialist nurse is already the prescribing expert, not the doctor whose name appears on the prescription. We have recommended that, in addition to supplementary nurse prescribers, specialist nurses with appropriate training and experience should have the opportunity to receive further training, enabling them to become independent prescribers in their specialist area. After a doctor has made the diagnosis, the higher level nurse prescriber would be qualified to draw up and review clinical management plans without necessarily consulting a doctor. We shall have to wait and see if our views are acted upon. NICE work Sarah O Brien, the Forum s deputy chair, has taken the lead for our work with the National Institute for Clinical Excellence (NICE). NICE, which was established in 1999 to provide authoritative and reliable guidance on healthcare for patients, healthcare professionals and the wider public, has commissioned guidelines in several areas of diabetes care, to complement the diabetes National Service Framework. Sarah has coordinated comments on the proposed scope of NICE s search for evidence of the clinical and cost-effectiveness of models for educating people with Type 1 and Type 2 diabetes. (The planned date for publication of the completed guideline is March 2003.) We are also contributing to the development of a guideline for the diagnosis and management of type 1 diabetes in primary and secondary care. Work was begun on this major task in April 2002, and comprehensive clinical guidelines are due to be launched in early A project manager and team of guideline development methodologists will gather the scientific evidence on all aspects of treatment and monitoring of type 1 diabetes, and present it for evaluation to the multidisciplinary members of the Guideline Development Group (including patient/carer representatives) at regular intervals. Sarah will provide most of the nursing input to this group, communicating with Forum committee members and others, to ensure that her contributions are as representative as possible. Competencies in diabetes nursing Margaret Tipson is our lead on the UK-wide project, guided by Dr Kim Manley of the RCN Institute, to define an integrated career and competency framework for diabetes nursing. The political context for this work comes from proposals outlined in the government white papers, Making a difference (July 1999) and Agenda for change (September 1999). Making a difference introduced the government s plan to create a new career framework (healthcare assistant, registered practitioner, expert practitioner and nurse consultant) to replace clinical grades for nurses, midwives and health visitors. Agenda for change announced the proposal to develop individual pay spines for doctors, dentists, healthcare assistants, nurses and professions allied to medicine. The government s aim is that all NHS staff will receive equal pay for work of equal value, whichever region they work in. Benchmarks will therefore be required, to clearly define the skills and competencies at each level of the pay spine, so that career progression can be based on responsibility, competence and satisfactory performance. Please send comments on either of these topics to Karibu01@globalnet.co.uk or to the RCN Diabetes Forum, c/o Anne Elliott, 20 Cavendish Square, London W1M 0AB Marilyn Gallichan, Chair karibu01@globalnet.co.uk The Royal College of Nursing: The Voice of Nursing 20 Cavendish Square, London, W1M 0AB. Telephone Fax: Pract Diab Int July/August 2002 Vol. 19 No. 6 Copyright 2002 John Wiley & Sons, Ltd. 175