A measure of quality of life after abdominal surgery

Transcription

1 Quality of Life Research (2006) 15: Ó Springer 2006 DOI /s A measure of quality of life after abdominal surgery David R. Urbach 1,2, Julie L. Harnish 2, Jodi Herold McIlroy 3 & David L. Streiner 4 1 Departments of Surgery and Health, Policy and Evaluation, University of Toronto, Toronto, ON, Canada; 2 Division of Clinical Decision Making and Health Care, University Health Network, Toronto, ON, Canada; 3 Department of Medicine and the Wilson Centre for Research in Education, University of Toronto, Toronto, ON, Canada; 4 Kunin-Lunenfeld Applied Research Unit, Baycrest Centre for Geriatric Care, Department of Psychiatry, University of Toronto, Toronto, ON, Canada Accepted in revised form 24 January 2006 Abstract Objective: To develop a reliable and valid measure of short-term quality of life after abdominal surgery. Summary background data: A major limitation of clinical trials evaluating laparoscopic surgical procedures has been the lack of a measure of short-term quality of life after abdominal surgery. Methods: We used existing health status measures, focus groups, and semi-structured patient interviews to generate a prototype questionnaire of 51 items, which was administered to patients within 2 weeks after an abdominal surgical procedure. We used structural equations modeling to reduce the number of items, retaining the three items with the highest factor loadings on each of the factors that accounted for one or more eigenvalue. Results: We administered the prototype questionnaire to 500 patients (mean age [SD] 53.4 [16.0], 51.4% male, 73.0% inpatient) at a mean 4.1 days after an abdominal surgical procedure. Item reduction yielded an 18-item measure with 6 sub-scales. The final instrument demonstrated good model fit in relation to our hypothesized factors (root mean square error of approximation 0.085, goodness-of-fit index 0.89). Conclusions: We developed a reliable and valid 18-item, 6-subscale measure of health-related quality of life after abdominal surgery, for use as an outcome measure in studies comparing laparoscopic and conventional abdominal surgery. Key words: Factor analysis, Laparoscopic surgery, Measurement, Quality of life, Surgery Introduction Minimally invasive abdominal surgery, or laparoscopic surgery, has increased in popularity over the last 15 years. Technologies such as highintensity light sources, laparoscopes, and specialized instruments introduced into the abdominal cavity through small cannulas, have allowed surgeons to perform many intra-abdominal procedures without making a large incision in the abdominal wall [1]. Laparoscopic surgery was quickly perceived to represent a major advance over conventional surgery. Procedures such as removal of the gallbladder, once associated with a post-operative hospital stay of several days and a recovery period of weeks, became ambulatory procedures with patients returning to their usual activities by as early as one week after surgery. Because laparoscopic procedures generally take longer to perform than open procedures, the shortterm costs are higher than conventional procedures. However, most observers believed that the increased resource consumption of laparoscopic surgery would be offset by earlier discharge from hospital and productivity gains by earlier return to work. Surgeons and patients also expected that less pain and disability following laparoscopic surgery would result in better health-related quality of life in

2 1054 the post-operative period. Surprisingly, randomized trials comparing laparoscopic with open procedures for colectomy [2], inguinal hernia repair [3], and even cholecystectomy [4], have found only very small benefit in short-term quality of life. It is not clear whether the failure to identify a meaningful advantage in post-operative quality of life is related to the lack of appropriate measures of health-related quality of life for patients recovering from abdominal surgery, or whether in fact the shortterm advantages of laparoscopic surgery are much smaller than had been assumed. We sought to develop a measure of health-related quality of life specifically intended to measure quality of life after abdominal surgery. Our intention was to create an instrument that could be used as an outcome measure in clinical trials comparing laparoscopic and open surgical procedures. This paper describes the initial development of the instrument. Methods Conceptual framework We developed a conceptual framework for the constructs underlying health-related quality of life after abdominal surgery by semi-structured interviews with 21 inpatients recovering from abdominal operations, focus groups with nurses, physicians, physiotherapists, occupational therapists, and acute pain clinical nurse specialists [5]. We also reviewed existing generic and disease-specific measures of health-related quality of life. Based on this research, we constructed a conceptual framework for health-related quality of life after abdominal surgery, consisting of six health concepts: physical limitations, functional impairment, pain, visceral function, sleep, and psychological function. Item generation In light of the conceptual framework developed through our preliminary research, we drafted a set of potential items to be included in a novel measure of quality of life. We constructed the items as negative statements regarding respondents health, and used a 7-category Likert response scale, indicating levels of agreement ranging from Strongly Disagree to Strongly Agree, with a neutral Neither Agree nor Disagree category in the center. In drafting the items for the questionnaire, our intent was use language that permitted use of a uniform response scale, to reduce the chance of responding paradoxically to an item because it was formulated differently than a preceding item (for example, an item phrased as a positive statement about the respondent s health [ I am able to move easily ] following an item phrased as a negative statement [ I can not climb a flight of stairs ]). We developed a 51-item prototype questionnaire. Item reduction We administered the 51-item prototype questionnaire to persons recovering from abdominal surgical procedures done by general surgeons at 2 hospitals. Subjects were eligible to participate in the study if they were able to read and write English. We administered the long form questionnaire to each subject once, at varying times post-operatively to capture variation in quality of life. Some subjects completed the questionnaire while still in hospital, others completed it when they were home and returned it by mail. Subjects were not excluded if they had emergency procedures, or had sustained complications related to their surgery. Subjects who had completed a questionnaire were no longer able to participate in the study if they required a subsequent surgical procedure. We enrolled 500 subjects into the study, to ensure approximately 10 subjects per item which has been suggested as the number required to obtain stable results in factor analysis [6]. We performed exploratory and confirmatory factor analyses [7], using the FACTOR procedure in SAS version 8.2 (SAS Institute, Cary NC) and using structural equations modeling [8] with LIS- REL software version 8.5 (Scientific Software International, Lincolnwood IL). We reduced the number of items to include in the final measure by selecting the three items for each factor with the highest factor loading in the confirmatory factor analysis. In the confirmatory factor analysis, we tested the fit of items according to the conceptual framework of quality of life after abdominal surgery developed earlier. Goodness-of-fit was assessed using the root mean square error of approximation, root mean square residual, and the

3 1055 goodness of fit index [9]. Internal consistency reliability was measured using Cronbach s a coefficient [10]. Correlations between factors were estimated using the Pearson correlation coefficient. Proportions of categorical variables were compared using v 2 -tests, and means of continuous variables were compared using t tests. The research protocol was approved by the Research Ethics Boards of the University of Toronto and University Health Network. Results Conceptual framework Based on our semi-structured interviews, focus groups, and review of existing quality of life measures, we identified six domains underlying healthrelated quality of life after abdominal surgery: physical limitations, functional impairment, pain, visceral function, sleep, and psychological function [5]. We developed a 51-item long form questionnaire, which we administered to 500 subjects. Study participants Study subjects were approximately equally split between men and women (Table 1). The age of subjects ranged between 14 and 91 years (mean 53.4). The questionnaires were completed between 1 and 15 days after surgery (mean 4.1). Seventythree percent of subjects were inpatients, and 35% had a laparoscopic operation. Sixty-five percent of subjects who had a laparoscopic procedure were women, as compared with 40% of subjects who had an open procedure (p<0.001). This difference was due to the fact that most laparoscopic operations were cholecystectomies, which are more commonly performed in women than in men. The mean age of the subjects who had a laparosocopic operation was 55 years, as compared with 51 for subjects who had open surgery (p=0.31). Factor analyses There were six factors with eigenvalues of one or greater. 11 of the 51 items were eliminated because respondents did not use the full response scale, the items were factorially complex, or because their inclusion decreased the reliability coefficient of the model. Factor loadings for the retained 40 items are presented in Table 2. We further reduced the number of items to include on the final questionnaire by retaining the three items with the highest factor loadings on each factor (Table 3). The goodness of fit of the reduced 18 variable model was better than the initial 40 variable model, with measures of goodness of fit in the reduced model indicating good data-to-model fit. The root mean square error of approximation was 0.11 in the initial model and in the reduced model (values less than 0.10 indicate good fit). The root mean square residual was 0.09 in the initial model and 0.05 in the reduced model (values less than 0.05 indicate good fit), and the goodness of fit index was 0.66 in the initial model and 0.89 in the reduced model (values 0.90 or greater indicate good fit). Some of the factors representing the sub-scales of our final measure were correlated with each other (Table 4). For example, physical limitations and functional impairment were highly correlated (0.91). Sleep had little correlation with physical limitations (0.49), pain (0.52) and functional impairment (0.53). The final instrument is presented in the appendix. Reliability analysis The reliability coefficients were good for five of the six subscales, with Cronbach s a ranging from 0.80 (sleep) to 0.90 (functional impairment, Table 5). The reliability coefficient of the visceral function subscale was low (0.55). Table 5 also presents the number of subjects who responded to each variable, and the means and standard deviations for the items, subscales, and for the total score. Discussion One of the most surprising developments to emerge from large randomized trials of laparoscopic surgical procedures was the recognition that the benefit of laparoscopic surgery, in terms of short-term quality of life, was far smaller than most observers had suspected. There are two potential explanations for this finding. First, it is

4 1056 Table 1. Characteristics of study subjects who completed the long form (51-item) questionnaire Variable Value Gender number (%) Male 257 (52) Female 241 (48) Age (in years) Mean (SD) (15.96) Range Number of days after surgery Mean (SD) 4.12 (2.61) Range 1 15 Status at time of questionnaire completion, number (%) Inpatient 365 (73) Outpatient 135 (27) Type of procedure, number (%) Open 326 (65) Laparoscopic 174 (35) SD denotes standard deviation. possible that there in fact is very little difference in postoperative quality of life between laparoscopic or open surgery, in contrast to the perceptions of most physicians and patients. Second, it is possible that there is a clinically meaningful benefit of laparoscopic surgery in terms of short-term quality of life, but currently available instruments are unable to detect it [11]. In the absence of studies using a measure of quality of life specifically intended to measure health after abdominal surgery, this will remain an open question. Outcome measures used in the short-term evaluation of surgical procedures have been broadly categorized into patient focused measures (clinical outcomes including symptoms and functional status, length of hospital stay, time to return to usual activity, satisfaction, and healthrelated quality of life), and organization focused measures (cost, satisfaction, length of stay, and hospital readmission) [12]. Outcome measures used in the evaluation of surgical procedures include utilization measures (such as cost or other measures of resource consumption, duration of operation, length of hospital stay, hospital readmission), clinical measures (such as symptoms, analgesic requirements), traditional measures of convalescence (such as time to return to work, time to resumption of usual activity), and functional status/health-related quality of life measures. Utilization measures have been extensively cited in evaluative research on surgical procedures [13 19]. However, these measures do not necessarily capture the effects of health outcomes that are meaningful to patients. Traditional clinical outcome measures, such as operative complications and assessment of pain in terms of analgesic requirements or simple measures (such as visual analogue scales), are also frequently reported short-term outcomes of surgical procedures. There are several problems with the use and interpretation of these clinical measures. Many surgical complications, such as surgical wound infection and pneumonia, lack universally accepted diagnostic criteria and are subject to considerable measurement error. Measures of convalescence, such as the time required for patients to return to their work or usual activities, have traditionally been emphasized in studies of elective surgical procedures such as inguinal hernia repair. However these measures perform poorly as indicators of postoperative functional status [20, 21], and are confounded by factors such as disability compensation [22]. Clinical trials have used various measures to compare health-related quality of life after laparoscopic or open surgical procedures [2, 3]. To date, there is no measure that captures all the relevant dimensions of health-related quality of life after abdominal surgery. While there are valid, reliable and responsive measures of functional status [23] and pain [24] after inguinal hernia surgery, they may not be appropriate for other abdominal operations and do not completely capture the multi-dimensional nature of healthrelated quality of life impairment after abdominal surgery. Other measures used in trials comparing surgical procedures for colon cancer had poor responsiveness to detect clinically important change [2, 11]. We developed a measure of short-term healthrelated quality of life for persons recovering from abdominal surgical procedures. The measure has 6 domains and 18 items. The overall scale has excellent reliability, and five of the six subscales have excellent internal consistency reliability. The measure also has evidence of construct validity, in that

5 1057 Table 2. Confirmatory factor structure of 40 variable model Item Factor 1 Factor 2 Factor 3 Factor 4 Factor 5 Factor 6 Physical limitations Functional impairment Pain Visceral function Sleep Psychological function Move 0.88 Stand 0.84 Climb 0.80 Walk 0.80 Sit 0.79 In/out bed 0.79 Reach 0.78 Self-care 0.91 Dependent 0.91 Get dressed 0.85 Wash body 0.85 Wash hair 0.84 Weak 0.75 On/Off Toilet 0.75 Appearance 0.74 Daily Activities 0.67 Leisure Activities 0.63 Abdominal pain 0.84 Movement pain 0.79 Incision pain 0.79 Pain meds 0.76 Pain when cough 0.76 Open incision 0.63 Bowels 0.76 Appetite 0.70 Thirsty 0.65 Cough 0.55 Nauseated 0.50 Urinate 0.49 Unable to eat 0.42 Tired 0.40 Trouble fall asleep 0.81 Wake at night 0.79 Not refreshed 0.70 Sleep position 0.55 Sleep medication 0.55 Concentration 0.79 Anxious 0.74 Helpless 0.68 Recovery time 0.52 This confirmatory factor analysis was done using structural equations modeling with LISREL software. The factors specified in the confirmatory factor analysis were those defined according to the focus groups and patient interviews. the data fit our hypothesized conceptual framework of quality of life after abdominal surgery. The internal consistency reliability of the visceral function subscale of our measure was low. This may be largely explained by the fact that in contrast to the other scales, which relied on multiple items to sample a similar construct, the visceral function scale was constructed from heterogeneous concepts such as gastrointestinal function, urinary function, and thirst. Scales developed to measure heterogeneous concepts may lack internal consistency [25], but may still be reliable according to other measures of reliability, such as test retest reliability [26]. We do not regard the lack of internal consistency of this subscale as a major impediment to measuring and reporting values on this subscale. Further research is required to study other aspects of

6 1058 Table 3. Confirmatory factor structure of 18 variable model Item Factor 1 Factor 2 Factor 3 Factor 4 Factor 5 Factor 6 Physical limitations Functional impairment Pain Visceral function Sleep Psychological function Move 0.86 Climb 0.83 Stand 0.81 Self-care 0.93 Dependent 0.91 Get dressed 0.85 Abdominal pain 0.85 Incision pain 0.79 Movement pain 0.77 Thirsty 0.67 Appetite 0.54 Bowels 0.48 Not refreshed 0.85 Wake at night 0.79 Trouble fall asleep 0.73 Helpless 0.86 Anxious 0.80 Concentration 0.74 Table 4. Factor correlation table for 18-item questionnaire Physical limitations Functional impairment Pain Visceral function Sleep Psychological function Physical limitations 1.0 Functional impairment Pain Visceral Function Sleep Psychological Function Values are Pearson correlation coefficients. reliability that may support the use of this subscale as a useful measure. Two of the subscales on the measure, physical function and functional limitations, were relatively correlated as compared with the other four subscales. Despite the degree of correlation, however, these two factors are conceptually distinct. In this measure, physical function refers to the extent to which a person s health affects performance of fundamental physical maneuvers. In contrast, functional limitations refer to the extent to which a person s health affects their ability to perform specific activities. In previous research using qualitative methods to develop a conceptual framework, these two concepts emerged as empirically distinct health domains. Further research is also necessary to assess the construct validity of the measure, evaluate its responsiveness and discriminatory ability, and to correlate values with well-understood health states, so a minimal clinically important difference can be defined for use in the design of clinical trials. In summary, we developed a measure of shortterm health-related quality of life after abdominal surgery that is intended for use as an outcome measure in clinical trials comparing conventional and laparoscopic operations for diseases such as colorectal cancer. Our measure is reliable, and has evidence of construct validity. Further evaluations of the construct validity and responsiveness of the measure, as well an estimates of normative values

7 1059 Table 5. Sub-scale scores and reliability analysis Subscale Item N Mean* SD Cronbach s a a Physical limitations Climb Move Stand Functional impairment Get dressed Self-care Dependent Pain Movement pain Abdominal pain Incision pain Visceral Function Bowels Thirsty Appetite Sleep Not refreshed Trouble fall asleep Wake at night Psychological function Concentration Helpless Anxious Overall score N Mean b SD Cronbach s a N denotes the number of subjects who responded to that item; SD denotes standard deviation. *Summative scores for the subscales ranged from 3 to 21, with higher scores indicating better quality of life. Item scores ranged from 1 to 7, with higher scores indicating better quality of life. a Cronbach s a for items is the reliability coefficient if the item is deleted. b The summative scores for the scale ranged from 18 to 126, with higher scores indicating better quality of life for well-understood health states, are necessary before using this new instrument as an outcome measure in clinical trials. Acknowledgements Supported by the physicians of Ontario through the Physicians Services Incorporated Foundation, the Canadian Association of General Surgeons, Cancer Care Ontario, and the Surgical Infection Society. Dr Urbach is a Career Scientist of the Ontario Ministry of Health and Long-Term Care, Health Research Personnel Development Program, and holds the Tyco Chair of Minimally Invasive Surgery at the University Health Network.

8 1060 Appendix Table A1. Abdominal surgery impact scale I cannot climb a flight of stairs Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I am not able to move easily Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I am not able to stand comfortably for five minutes Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree It is difficult for me to get dressed Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I am unable to care for myself Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I feel dependent on others to care for me Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I am afraid to move because it might cause pain Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I have severe pain in and around my abdomen Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree My incision(s) is/are causing me pain Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I am not able to move my bowels normally Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I am uncomfortable because I am thirsty Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I do not have a good appetite Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I wake up feeling that sleep has not refreshed me Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I have trouble falling asleep Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I wake up a lot in the night Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I have difficulty concentrating on what I am doing Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree (conversation, watching TV, or reading) I feel helpless Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree I feel anxious Strongly agree Agree Somewhat agree Neither agree nor disagree Somewhat disagree Disagree Strongly disagree This questionnaire contains a number of statements that describe ways in which your abdominal surgery might have affected you. Please circle the most appropriate number to indicate the degree to which you agree or disagree with each statement. If you are unsure about how to answer a statement, please give the best answer you can. When answering each question, please think about how you have been feeling over the past day (24 hours).

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