Depression in Diabetes Self-Rating Scale: a screening tool

Andrzej Kokoszka ORIGINAL II Department of Psychiatry, Medical University of Warsaw, Poland Depression in Diabetes Self-Rating Scale: a screening tool Abstract Background. Early diagnosis and treatment of depressive symptoms in diabetic patients not only improves their well being but also reduces the risk of complications. Method. Due to the unique nature of complaints in this patient population, a special six-item self-rating scale has been developed to facilitate the diagnosis of depressive symptoms during routine medical evaluations. Results. Despite its brevity, the scale has demonstrated relatively good reliability (Cronbach s alpha = 0.81) and validity (showing Pearson s coefficients of correlation [r] with Beck Depression Inventory score, Depression Scale of Hospital Anxiety and Depression Scale and Hamilton Depression Rating Scale of 0.72, 0.68 and 0.68, respectively). Sten norms have been developed. Conclusions. The scale has shown good psychometric properties and may be used during routine medical evaluations. Diabet Dośw i Klin 2008; 8: 43 47 key words: diabetes mellitus, depression, self-rating scale, screening Introduction Development of depression by patients with diabetes mellitus is associated with a higher risk of complications [1] and death [2, 3] and with elevated glycated haemoglobin [4]. Development of depressive episodes is associated with a lower physical activity, poorer compliance and improper diet [5]. Depression, even at the subclinical level, is important to the development of diabetic complications. The risk of macroangiopathy in patients with depressive symptoms compared to patients without these symptoms is twice as high. The risk of microangiopathy is even higher: 2.3% in patients without depressive symptoms, 8.6% in patients with subclinical depression and 11.3% in patients with symptoms of clinical depression [6]. In the context of these data it is alarming that study results suggest that 40% of diabetic patients demonstrate elevated level of depressed mood, although not all these patients meet the diagnostic criteria for clinical Address for correspondence: Andrzej Kokoszka, MD, PhD Second Clinic of Psychiatry, Medical University of Warsaw ul. Kondratowicza 8, 03 242 Warsaw Tel/fax (+48 22) 326 58 92 e-mail: kokoszka@amwaw.edu.pl Diabetologia Doświadczalna i Kliniczna 2008, 8, 1, 43 47 Copyright 2008 Via Medica, ISSN 1643 3165 depression [7]. The incidence of depression that meets the diagnostic criteria is three times higher in diabetic patients than in the general population [8]. Results of meta-analyses of 39 studies demonstrate that the criteria for major depression are met by about 11% diabetic patients, and 31% show an increased severity of depressive symptoms on self-rating scales [9]. In this situation, the diagnosis of depressive disorders should be part of the routine medical evaluation. This may be facilitated by using short screening selfrating scales completed by the patients. The following tools available in Polish may be used to this end: Beck Depression Inventory (BDI) [10, 11]; Hospital Anxiety and Depression Scale (HADS) [12, 13]; WHO-Five Well-being Index (WHO-5) [www.cure4you.dk/354/who-5_polish.pdf]. Each of the above tools has considerable limitations. None of them contains norms for the Polish population and does not take into account the uniqueness of depressive symptoms in diabetic patients, characterised by treating the depressed mood as a natural consequence of having diabetes and by not recognising depressive symptoms as a separate illness. In addition, BDI is too long and the statements it contains are not easy to understand by older patients. By definition, HADS does not take into account the unique features of outpatients. WHO-5 primarily concerns the quality of life and no data are available on the reliability and validity of the Polish version of this tool. Given these circumstan- www.ddk.viamedica.pl 43

Diabetologia Doświadczalna i Kliniczna 2008, Vol. 8, No. 1 ces there is a need to develop a short tool supporting the detection of depressive symptoms in patients with diabetes mellitus. The aim of this paper is to present the Depression in Diabetes Self-Rating Scale, its design and psychometric properties. Method Development of the Depression in Diabetes Self-Rating Scale Recognising the fact that the symptoms reported by patients with depression in the course of diabetes mellitus have unique features, we conducted group and individual interviews with diabetic patients with and without symptoms of depression. Based on the replies provided by these patients, we compiled a list of 31 statements used in further studies to obtain a short list of statements which provide good differentiation between diabetic patients with depressive symptoms and diabetic patients without depressive symptoms. Examination of the preliminary, long form, containing 31 sentences along with the five-item Likert-type rating scale, was conducted in 240 diabetic patients (124 women and 116 men between 20 and 89 years of age (mean age = 56 years, SD = 13.91 years) with the duration of diabetes ranging from less than 1 year to 37 years (mean = 8.26 years; SD = 5.56 years). Fifty-one patients (23.4%) had completed primary education, 132 patients (60.6%) had completed secondary education and 35 patients (16.1%) had a college or university education. Selection of 6 statements for the final version of the scale (Table 1) was based on the results of the analysis of regression in relation to the overall BDI and HADS scores, completed at the same time by the study subjects, and the Hamilton Depression Rating Scale (HDRS) scores [14 17]. Psychometric properties of the Depression in Diabetes Self-Rating Scale The reliability and validity of the scale and the preliminary sten norms (Table 2) were calculated in consecutive examinations performed in 101 patients (51 men and 50 women) with type 2 diabetes mellitus between 28 and 82 years of age (mean age = 63.18 years, SD = 10.74 years) managed for diabetes for periods ranging from less than 1 year to 48 years (mean = 12.70 years, SD = 8.61 years). The mean severity of depressive symptoms was 11.92 (SD = 9.42) in Beck Depression Inventory with the normal score in the English version of 9 or less, 7.62 (SD = 7.39) on Hamilton Depression Rating Scale with the normal score in the English version of 7 or less, 11.05 (SD = 9.77) on Hospital Anxiety and Depression Scale with the normal score of 7 or less and mild depression rated as 8 to 10. Based on the comparison with norms for English-speaking populations, it may be assumed that the study group ranged between normal and mild depression. Analysis of the distribution of results suggested normal distribution (Z Kolmogorov-Smirnov = 1.31, P = 0.062), which additionally supports the use of the attached sten norms in the evaluation of depression in diabetic patients (Table 3). The threshold value indicating moderate depression largely reflects the norms for the English versions of the comparable scales. Hundred percent of the subjects achieving a score of 3 or more also achieve results indicating at least mild depression with 67.3% achieving results indicating this outcome in Beck Depression Inventory and Hamilton Depression Rating Scale. In light of this, it may be assumed that exceeding the score of 3 on the presented scale requires further diagnostic investigations to narrow down or rule out the diagnosis of one of the depressive disorders. Exceeding the threshold score of 7 stens, which is equivalent to the score of 11 on the Depression in Diabetes Self-Rating Scale, indicates a high risk of severe depression. Four out of 5 patients (80%) who exceeded the criterion of severe depression in Beck Depression Inventory (a score of more than 30) achieved a score of over 11 on the scale in question. All of the 8 patients (100%) who achieved a score of more than 19 on Hamilton Depression Rating Scale (severe and very severe depression) achieved a score of more than 11 on the Depression in Diabetes Self-Rating Scale. The reliability of the Depression in Diabetes Self-Rating Scale is high (Cronbach s alpha = 0.81). The scale also demonstrates a good validity, as measured by Pearson s coefficient of correlation with the overall BDI score (r = 0.72), overall HDRS score (r = 0.68) and the HADS score (r = 0.68). Results Discussion The scale presented in this paper is a simple tool to monitor the presence of depressive symptoms in patients with diabetes mellitus. While its completion by the patient and the calculation of results takes less than five minutes, the scale offers a relatively good opportunity to diagnose symptoms of depression. If these symptoms are found, further investigation is required and appropriate therapy must be proposed. Accurate diagnosis of one of the depressive disorders (depressive episode, dysthymia, cyclothymia, adaptation disorder, depressive disorder and mixed anxiety disorder, organic disorder) 44 www.ddk.viamedica.pl

Andrzej Kokoszka Depression in Diabetes Self-Rating Scale Table 1. Depression in Diabetes Self-Rating Scale with the key* Name and surname.. Data Below is a list of statements. Read them carefully and answer the following questions as honestly and accurately as you can, taking into account the past week, by crossing out one of the five options. There are no good and bad answers. The aim of this questionnaire is to accurately analyse your feelings associated with the disease, which will be very important to the treatment guided by them. 1. Despite my diabetes I cope pretty well in life 2. I often feel pleasure in everyday life 3. I often feel I would be ready to take additional medication to considerably reduce my depressed mood 4. I do not cope with my life 5. I generally feel happy and my diabetes has little effect on my well-being 6. When I think about my disease, I feel like crying Key Questions 1, 2 and 5: I fully agree = 0, I partially agree = 1, Hard to say = 2, I partially disagree = 3, I fully disagree = 4 Questions 3, 4 and 6: I fully agree = 4, I partially agree = 3, Hard to say = 2, I partially disagree = 1, I fully disagree = 0 *Polish version of the scale is available on the request from the author by a post letter or e-mail: kokoszka@amwaw.edu.pl www.ddk.viamedica.pl 45

Diabetologia Doświadczalna i Kliniczna 2008, Vol. 8, No. 1 Table 2. Preliminary sten scale: method for accurate transformation of raw data into standardised results Raw result f Cf cf*1/n Sten 24 1 101 1.000 10 22 1 100 0.990 10 21 1 99 0.980 10 19 1 98 0.970 9 18 2 97 0.960 9 17 2 95 0.941 9 16 2 93 0.921 8 15 2 91 0.901 8 14 6 89 0.881 8 13 5 83 0.822 7 12 4 78 0.772 7 11 5 74 0.733 7 10 4 69 0.683 6 9 6 65 0.644 6 8 5 59 0.584 6 7 5 54 0.535 6 6 5 49 0.485 5 5 3 44 0.436 5 4 8 41 0.406 5 3 7 33 0.327 5 2 10 26 0.257 4 1 3 16 0.158 3 0 13 13 0.129 2 Source of the range of values of cf*1/n: Dobruszek [19] Table 3. Simplified method of transforming raw data into standardised results and the principles of interpretation of results The tool in question has a certain limitation in that the sten norms have been developed on the basis of 101 patients. However, the normal distribution of the results and the relatively high correlations of threshold values with the commonly used, although much more time-consuming analogous values enable cautious use of the proposed norms. Development of final sten norms would require a considerable delay in the publication of the scale, due to the absence of other depression rating scales having norms for the Polish population, which could be used as adequate and fully comparable. An additional argument supporting the publication of preliminary sten norms is the fact that this tool is merely intended as a screening tool. As such, it may facilitate identification of patients with depressive symptoms and in the case of a score below sten 3, it would be a good idea to use an additional screening test by asking the following two questions: Have you experienced the feeling of depression or hopelessness in the past month? Have you often experienced loss of interest or pleasure when performing various activities in the past month? Studies indicate that positive answer to both questions carries a sensitivity of 97% and specificity of 67% in diagnosing depression compared to the computerised version of the standardised interview (Composite International Diagnostic Interview) [18]. A score above 11 requires intensive diagnostic evaluation, including suicide risk assessment. Raw result zsten Conclusions 0 1 2 1 3 2 4 From 3 to 6 5 From 7 to 10 6 From 11 to 13 7 From 14 to 16 8 From 17 to 19 9 From 20 to 24 10 Simplifying the results it may be said that: scores from 0 to 2 (stens 1 to 4) should be interpreted as low severity of depression scores from 3 to 10 (stens 5 to 6) should be interpreted as moderate severity of depression scores from 11 to 24 (stens 7 to 10) should be interpreted as high severity of depression may be made, depending on the level of competence, by the diabetologist or a psychiatrist collaborating with the diabetologist. The six-item self-rating scale of depression in diabetes is characterised by high reliability and validity. It is brief and may be used during routine medical evaluations. The existing sten norms enable it to be used for the detection of depressive disorders in diabetic patients. The study was conducted with the support from Novo Nordisk Pharma Sp. z o.o. References 1. De Groot M, Anderson R, Freedland KE, Clouse RE, Lustman PJ. Association of depression and diabetes complications: A meta-analysis. Psychosom Med 2001; 63: 619 630. 2. Egede L, Nietert P, Zheng D. Depression and all-cause and coronary heart disease mortality among adults with and without diabetes. Diabetes Care 2005; 28: 1339 1345. 3. Katon WJ, Rutter, Simon G, Lin EH. et al. The association of comorbid depression with mortality in patients with type 2 diabetes. Diabetes Care 2005; 28: 2668 2672. 4. Gross R, Olfson M, Gameroff M. et al. Depression and glycemic control in Hispanic primary care patients with diabetes. J Gen Intern Med 2005; 20: 460 466. 46 www.ddk.viamedica.pl

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