What Score in WHODAS 2.0 12-Item Interviewer Version Corresponds to 40 % Psychiatric Disability? A Comparative Study Against IDEAS

  • Chethan Basavarajappa
  • Kailash Suresh Kumar
  • Vedalaveni Chowdappa Suresh
  • Channaveerachari Naveen Kumar
  • Vinutha Ravishankar
  • Umamaheswari Vanamoorthy
  • Urvakhsh Mehta
  • Avinash Waghmare
  • Sivakumar Thanapal
Original Article
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Abstract

World Health Organization (WHO) has developed WHO Disability Assessment Schedule (WHODAS 2.0) in line with International Classification of Functioning, Disability and Health (ICF) to assess disability across cultures and diseases. Universal usage of this instrument will synchronize disability data across various countries and help in international comparison. In this study, we sought to find out the cut-off point in WHODAS 2.0 12-item Interviewer Version that corresponds to the global score of 7 on Indian Disability Evaluation and Assessment Scale (IDEAS). This cut-off on IDEAS denotes 40 % disability, making patients eligible for social welfare benefits. Receiver operating characteristic (ROC) curve analysis showed that a score of 23 on WHODAS 2.0 12-item Interviewer Version corresponded to the global IDEAS score of 7 on using the Youden’s J static. Additionally, ROC curve showed that WHODAS is an accurate test to measure psychiatric disability.

Keywords

Disability evaluation Disability assessment IDEAS WHODAS 

Introduction

The International Classification of Functioning, Disability and health (ICF) marked a paradigm shift in concept of health and disability. Earlier, disability was considered to begin where health ended. People who were disabled were in a separate category.

ICF recognizes disability as the consequence of the interaction of the individual with an environment [1] that does not accommodate that individual’s differences and limits or impedes the individual’s participation in society. Thus, ICF shifts the focus from cause to impact. It places all health conditions on an equal footing allowing them to be compared using a common metric—the ruler of health and disability.

The 54th World Health Assembly (WHA) vide resolution WHA 54.21 urged member states to use ICF in research, surveillance and reporting [2]. 191 Member States of the WHO including India have agreed to adopt ICF as the basis for the scientific standardization of data on health and disability world-wide [2].

WHO Disability Assessment Schedule 2.0 (WHODAS 2.0) generically assesses health and disability as conceptualized by ICF. It was developed based on extensive cross cultural field studies across 19 countries including India. It is applicable across cultures and in all adult populations [3]. It can be used for all diseases including mental, neurological and addictive disorders. It has been used to assess disability [4] caused not only due to psychotic disorders [5], schizophrenia [6], bipolar disorders and depression [4], but also due to medical conditions like osteoarthritis, osteoporosis, rheumatoid arthritis [4], arthritis [7], ankylosing spondylitis [8], low back ache [9], ischemic heart disease, migraine, Parkinson’s disease, multiple sclerosis [4], systemic sclerosis [10], stroke [11], hearing loss [12], persons in rehabilitation [13]. There are multiple versions (12 and 36 item) which are available as interviewer, self or proxy administered forms. The 12-item version is helpful in briefly assessing and computing the overall functioning. It takes short time to administer [3].

Currently, each country has its own method of evaluating, quantifying and setting threshold of disability for availing disability benefits. Some countries depend on clinician’s judgment to certify disability and do not have a scale for the purpose.

India is among the countries which have adopted ICF as healthcare information technology (HCIT) standard for reporting data pertaining to functioning, disability and health [14]. But, existing Indian Government guidelines for evaluation of various physical disabilities and certification follow the earlier impairment based definition of disability (as per International classification of Impairment, Disability and Handicap). In contrast, Indian disability evaluation and assessment scale (IDEAS) is a futuristic instrument which evaluates the impact of the mental illness on various life domains to measure disability. The gazette version of IDEAS for measuring and quantifying disability due to mental illness incorporated some modifications to the original proposal made by taskforce of rehabilitation subcommittee of Indian psychiatric society [15]. It is a brief scale and takes a short time to administer. However, it is validated only in Indian setting.

In India, the minimum degree of disability to avail concessions/benefits according to Persons with disability act 1995 is 40 % [16, 17]. This corresponds to global IDEAS score of 7.

As India has agreed to adopt ICF as the basis for the scientific standardization of data on health and disability, there is an anticipated shift to WHODAS 2.0 which is a generic measure for health and disability due to all diseases including mental, neurological and addictive disorders.

To our knowledge, there is no published literature comparing IDEAS with WHODAS 2.0 for measuring psychiatric disability.

Objective of the Study

To find out score in WHODAS 2.0 12-item Interviewer Version which corresponds to 40 % psychiatric disability measured using IDEAS.

Methods

Setting and Sample

The study sample comprised patients with psychiatric disorders referred to Psychiatric Rehabilitation Services (PRS) of the National Institute of Mental Health & Neurosciences (NIMHANS), Bengaluru, India. Two kinds of patients attend PRS. Inpatients admitted under various adult psychiatry units of NIMHANS and day boarders who are out-patients who come in the morning and go back to their community in the evening. Both groups were recruited in the study to have a better representation of the population and not restrict to one kind.

Patients were recruited if they fulfilled the following inclusion criteria: persons who gave written informed consent, and who were accompanied by their family members. Persons with mental retardation were excluded (as IDEAS measures only psychiatric disorders). The patients were diagnosed by the adult psychiatry unit referring the patient to the day care centre using ICD 10. Information relevant for all the assessments was collected from both patients and their family members. 50 patients who fulfilled study inclusion criteria were recruited by convenience sampling. The same rater applied both IDEAS and WHODAS. Blinding was not done.

The study was carried out over 2 months, between January 2014 and March 2014. The study was approved by Institute Ethics committee.

Tools Used

Socio demographic and clinical details were noted in a semi-structured proforma designed for the purpose of this study.

WHODAS 2.0 12-Item Interviewer Version (WHODAS) [3]

It is a generic tool to assess health and disability developed by WHO. It is built upon the conceptual framework of ICF. It captures the level of functioning of a person in the past 30 days in six domains namely cognition, mobility, self-care, getting along, life activities and participation. Both are available to be rated by the patient, proxy and the interviewer. Test–retest reliability had an intra-class coefficient of 0.69–0.89 at item level; 0.93–0.96 at domain level; and 0.98 at overall level [3]. It also has good face validity (65 % of the experts had opined that it measures disability as defined by ICF); concurrent validity (correlation coefficients between 0.45 and 0.65 with Functional Independence Measure, London Handicap Scale, Medical Outcomes Study 12-Item Short-Form Health Survey, Medical Outcomes Study 36-Item Short-Form Health Survey, WHO Quality of Life Project); and construct validity (significantly picked up sensitivity to change) [3]. The 12-item version explains 81 % of the variance of the 36-item version. The 12-item version is useful for brief assessments and takes about 5 min to administer [3]. This was administered on patients.

Indian Disability Evaluation and Assessment Scale (IDEAS) [15]

IDEAS is used to measure disability caused due to psychiatric disorders. It is a five items scale and each item is scored from 0 to 4. It measures disability in four domains: self-care, interpersonal activities, communication and understanding and work. Duration of illness (DOI) has been given weightage as well. Global IDEAS score is obtained by adding the individual item scores and the score for the DOI. The scale has been shown to have good internal consistency (the Cronbach’s alpha = 0.708) and good construct validity (good correlation of global IDEAS score with negative subscale (r = 0.607, p = 0.001) and total PANSS scores (r = 0.5, p = 0.001); and with total WHOQOL scores (r = −0.356, p = 0.001) in patients with residual schizophrenia [18]. IDEAS was administered on patients.

Statistical Analyses

GNU PSPP Statistical Analysis Software 0.9.0-g745ee3 was used for the analyses [19]. The demographic and clinical characteristics were represented using descriptive statistics. Pearson Correlation (2-tailed) was used to measure correlation between IDEAS and WHODAS with significance at the 0.01.

The receiver operating characteristic (ROC) curve [20] (see Fig. 1) was used for the following two purposes.
Fig. 1

ROC curve. Diagonal segments are produced by ties

  1. 1.

    To find the cut-off score on WHODAS, above which patients could be categorized as ‘disabled’

     

For this purpose, we used IDEAS as the gold standard. Patients with global IDEAS score of 7 or more (n = 27) were categorized as disabled. All others (n = 23) were considered ‘not disabled’. This categorical division was used as the ‘state-variable’ in the ROC analysis. Total WHODAS scores were used as the ‘test-variables’ (continuous variables). The resultant ROC Curve was analysed [21]. Youden’s J static/Youden’s index was used to find out the optimum cut-off score of WHODAS [22, 23, 24].

The ROC curve plots true positive rate (TPR; sensitivity) against the false positive rate (FPR; 1 − specificity) for the different possible cut-points from the test-variables mentioned above [21].

Youden’s J static is considered the best method to find out the optimal cut-point for a scale which does not have one [22, 23, 24]. J = sensitivity + specificity − 1 [21, 22] or J = TPR − FPR [23, 24]. The value of J ranges from 0 to 1. The value 0 means that the test is useless and the value 1 means that the test is perfect [22, 23, 24]. Hence the values nearer to 1 predict better cut-off value.

The cut-off value for WHODAS scale was arrived at as follows. Total WHODAS scores ranged between 12 and 47 in our sample. For each decimal in this range, the sensitivity (TPR), 1 − specificity (FPR) and the J (TPR–FPR) were computed (see Table 1). The WHODAS score that corresponded to the maximum J static value was taken as the cut-off for categorizing patients as disabled.
Table 1

Coordinates of the curve and Youden’s index (J)

‘Disabled’ if greater than or equal toa

Sensitivity (TPR)

1 − specificity (FPR)

J = TPR − FPR

12.5000

0.963

0.783

0.18

13.5000

0.963

0.739

0.224

15.0000

0.926

0.696

0.23

16.5000

0.889

0.522

0.367

17.5000

0.852

0.478

0.374

18.5000

0.852

0.391

0.461

19.5000

0.852

0.348

0.504

21.0000

0.778

0.217

0.561

22.5000

0.741

0.130

0.611

23.5000

0.704

0.130

0.574

24.5000

0.667

0.130

0.537

25.5000

0.630

0.130

0.5

26.5000

0.593

0.130

0.463

27.5000

0.519

0.130

0.389

28.5000

0.407

0.043

0.364

29.5000

0.370

0.043

0.327

31.0000

0.296

0.000

0.296

33.0000

0.222

0.000

0.222

34.5000

0.148

0.000

0.148

36.5000

0.111

0.000

0.111

39.0000

0.074

0.000

0.074

43.0000

0.037

0.000

0.037

47.0000

0.000

0.000

0

Test result variable(s): WHODAS 2.0 12-item interviewer version total score

The highest J-static value for coordinates of the ROC Curve is mentioned in bold

aThe smallest cut-off value is the minimum observed test value minus 1, and the largest cut-off value is the maximum observed test value plus 1. All the other cutoff values are the averages of two consecutive ordered observed test values

  1. 2.

    To find out the accuracy of the test

     

After finding out the cut-off, we used the ROC curve to find out the accuracy of the test. We did this in two ways.

Accuracy was measured by the computing the Area under the Curve (AUC). AUC 0.9–1 is excellent, 0.8–0.9 is good, 0.7–0.8 is fair, 0.6–0.7 is poor and 0.5–0.6 is fail [20, 21].

Accuracy was also understood by seeing how the curve was positioned. The closer the curve follows the left and then top border, the more accurate the test is. The closer the curve to the 45° line, the lesser accurate the test is [20].

Results

The mean age of the sample was 32.5 years and mean education was 10.9 years. They were predominantly urban males from above poverty line socio economic status (see Table 2). The mean age of onset of illness was 23.9 years. Duration of untreated illness was 18.2 months and the total duration was 77.6 months. Majority had psychotic spectrum of disorders (psychotic spectrum consisted of schizophrenia, persistent delusional disorders, acute and transient psychotic disorders, schizoaffective disorders, non-organic psychotic disorders; see Table 3). 27 persons scored ≥40 % in IDEAS (considered disabled). IDEAS Global Scores and WHODAS correlated well (r2 = 0.73; p < 0.01).
Table 2

Socio-demographic details

Variable

Mean (SD) or N (%)

Age (years)

32.5 (9.9)

Education (years)

10.9 (4.1)

Gender

 Male

31 (62)

 Female

19 (38)

Socio-economic status

 Below poverty line

18 (36)

 Above poverty line

32 (64)

Location

 Rural

14 (28)

 Urban

36 (72)

Table 3

Illness variables

Variable

Mean (SD) or N (%)

Age at onset (years)

23.9 (8.8)

Duration of untreated illness (months)

18.2 (35.8)

Duration of illness (months)

77.6 (91.9)

WHODAS 2.0 scores

23.0 (8.3)

IDEAS scores

7.3 (3.8)

Psychotic spectrum

33 (66)

Anxiety spectrum

2 (4)

Bipolar affective disorders

11 (22)

Depression

4 (8)

The sample was divided into two groups namely ‘disabled’ and ‘not-disabled’ based on global IDEAS score >7 or <7 respectively. TPRs were plotted against and FPRs at different cut-offs of WHODAS as per details mentioned in the methods section. The resultant ROC curve (see Fig. 1) was analyzed.

Total WHODAS scores ranged between 12 and 47 in our sample. J-static values for coordinates of the ROC Curve in this range were calculated. The highest value obtained was 0.611 corresponding to the score of ≥22.5 i.e., 23 (next higher decimal) in WHODAS (see Table 1).

The AUC was 0.83 indicating that the accuracy of the test was good (see Table 4). The curve followed the left and then the top border, indicating that the test conducted (WHODAS) was accurate (see Fig. 1).
Table 4

Area under the curve

Area

0.830

Standard errora

0.059

Asymptotic significanceb

0.000

Asymptotic 95 % confidence interval

 Lower bound

0.715

 Upper bound

0.945

aUnder the nonparametric assumption

bNull hypothesis: true area = 0.5

Discussion

There are various instruments which are used to assess health status and disability across the world [2, 25, 26]; Developed countries collect data regarding disability by surveys and have higher prevalence of disability as compared to developing countries which collect data through census and have lower prevalence rates [27]. Many countries are in the process of implementing ICF to assess disability status of individuals for availing disability benefits [27, 28, 29, 30]. The Diagnostic and Statistical Manual of Mental Disorders (DSM) has started using WHODAS 2.0 in place of Global Assessment of Functioning (GAF) which was used in the earlier versions of DSM [31]. WHODAS 2.0 is expected to become the world standard for disability data and social policy modelling [1].

As a disability measurement tool, IDEAS shares some advantages with WHODAS 2.0 in terms of ease of use and measuring disability in terms of impact of mental illness on life domains. Like IDEAS, WHODAS 2.0 12 item version is also easy to administer and can be completed in about 5 min. Unlike WHODAS 2.0, IDEAS considers duration of illness and home makers in work domain. Many items in WHODAS 2.0 are not relevant to mental disorders (like standing, walking for a long distance) as it is constructed to be used across all health conditions. But, WHODAS 2.0 has the distinct advantage of being a generic instrument to measure health and disability across cultures for all health conditions.

WHODAS 2.0 has been used to assess disability in persons with mental illness [3, 4, 5]. The present study reports the results of WHODAS with mental illness in Indian setting. It is easy to administer, can be completed in 5 min and can be used in busy clinical settings.

Adoption of WHODAS 2.0 in India will be helpful to health professionals and administrators to measure health and disability according to ICF irrespective of nature of health conditions. The data will shed light on standardized disability levels and profiles across different health conditions.

As cross-national variations exist in the norms for disability measures, studies to find country specific normative data have been recommended to facilitate use of WHODAS 2.0 in clinical and epidemiological research [32]. Large scale studies in community samples can generate normative data for the country which can help in determining the threshold for availing concessions/welfare benefits. According to existing 40 % threshold in IDEAS for availing concessions/benefits as a person disabled with mental illness, WHODAS cut-off score to qualify a person with mental illness for disability benefits is 23.

It will also help compare health and disability data across countries using a common measure. It will be helpful in knowing the impact of public policies, poverty and prevention programs on persons with disability [27].

The study limitations are small sample size, convenience sampling and unblinded rater. Studies on larger sample size representative of patient population is necessary.

However, the sample included a variety of diagnoses and; disabled as well as non-disabled population.

Conclusions and Future Directions

Normative data for India needs to be studied. Similar studies with larger sample sizes in community settings with blinded raters needs be done.

Studies across the globe using a cross-culturally accepted tool like WHODAS 2.0 will be useful in standardizing date about health and disability across the world, evaluate health settings that deal with disability, and help in health economics.

Copyright information

© Springer India Pvt. Ltd. 2016

Authors and Affiliations

  • Chethan Basavarajappa
    • 1
  • Kailash Suresh Kumar
    • 2
  • Vedalaveni Chowdappa Suresh
    • 2
  • Channaveerachari Naveen Kumar
    • 2
  • Vinutha Ravishankar
    • 2
  • Umamaheswari Vanamoorthy
    • 2
  • Urvakhsh Mehta
    • 2
  • Avinash Waghmare
    • 1
  • Sivakumar Thanapal
    • 1
  1. 1.Psychiatric Rehabilitation Services, Department of PsychiatryNational Institute of Mental Health and Neurosciences (NIMHANS)BengaluruIndia
  2. 2.Department of PsychiatryNational Institute of Mental Health and Neurosciences (NIMHANS)BengaluruIndia

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