Arthritis & Rheumatism (Arthritis Care & Research) Vol. 49, No. 5S, October 15, 2003, pp S85 S89 DOI 10.1002/art.11403 2003, American College of Rheumatology MEASURES OF FUNCTION Measures of Adult Work Disability The Work Limitations Questionnaire (WLQ) and the Rheumatoid Arthritis Work Instability Scale (RA-WIS) Saralynn H. Allaire WORK LIMITATIONS QUESTIONNAIRE (WLQ) General Description Purpose. To measure on-the-job impact of chronic health problems and/or treatment and health-related productivity loss (1). Content. Items address limitations in performing 4 dimensions of job demands (see subscales). Items are common attributes of job roles, are sensitive to the effects of physical and/or mental health problems, and relevant to productivity. Developer/contact information. Debra Lerner, PhD, The Health Institute, Tufts-New-England Medical Center, Division of Clinical Research, Box 345, 750 Washington Street, Boston, MA 02111. E-mail: wlq@tufts-nemc.org. Items may be seen in the Lerner et al publication (1). Versions. English and Spanish; pencil and paper, telephone, and internet; a short form that measures productivity limitations only is being developed. Number of items in scale. There are 25 items. Subscales. The WLQ contains 4 different scales, physical demands, time demands, mentalinterpersonal demands, and output demands. Physical Demands: 6 items that cover ability to perform job tasks involving bodily strength, movement, endurance, coordination, and flexibility (2); examples are walk or move around different Supported by grant P60-AR-47785. Saralynn H. Allaire, ScD: Boston University School of Medicine, Massachusetts. Address correspondence to Saralynn H. Allaire, ScD, Boston University School of Medicine, Clinical Epidemiology Research and Training Unit, A203, 715 Albany Street, Boston, MA 02118. E-mail: sallaire@bu.edu. Submitted for publication March 28, 2003; accepted April 4, 2003. work locations (for example, go to meetings) and use hand-held tools or equipment (for example, phone, pen, keyboard, computer mouse, drill, hairdryer, or sander). Time Demands: 5 items that address handling a job s time and scheduling demands (2); examples are work the required number of hours and stick to a routine or schedule. Mental-Interpersonal Demands: 9 items that address cognitively-demanding tasks (2) like keep your mind on your work and on-the-job social interactions like control your temper around people when working. Output Demands: 5 items that concern reduced productivity (2), such as handle the workload and do your work without making mistakes. Populations. Developmental/target. Employed persons with chronic health conditions. Individuals with asthma, Crohn s disease, liver disease, depression/anxiety or epilepsy generated items for the instrument; validity testing was conducted in multiple patient groups (e.g., persons diagnosed with rheumatoid arthritis, chronic daily headaches, epilepsy, osteoarthritis, or depression) and in employee populations within large firms. Other uses. Since development, the instrument has been used in samples of people with rheumatoid arthritis (3,4), fibromyalgia (5), depression, low back pain (6), chronic pain, head trauma, and other conditions. It is being used in academic and industry-sponsored clinical trials (7), and some employers are using it to assess employee populations. WHO ICF Components. Activity limitation, Participation restriction. Administration Method. Self-report questionnaire. Training. None required. S85
S86 Allaire Time to administer/complete. 10 minutes. Equipment needed. No special equipment needed. Cost/availability. Provided free of charge for non-commercial applications. Copy available at the Arthritis Care & Research website at http://www.interscience.wiley.com/jpages/0004-3591:1/suppmat/index.html. Scoring Responses. Scale. Each item has a 5-point ordinal response scale; there is an additional category of response (the sixth point) for does not apply to my job. Score range. Range is 0 100%; 0% health makes the job demand difficult none of the time and 100% health makes the job demand difficult all of the time. Interpretation of scores. Cut points have not been established; however, a nationally representative household survey will be conducted in 2002 by the National Opinion Research Center, which will generate normative WLQ data for various condition groups, including persons with musculoskeletal symptoms. Method of scoring. The instrument can be scored by hand. The WLQ generates 4 scales. All items are scored as follows: 0 0% (none of the time); 1 25%; 2 50%; 3 75%; and 4 100% (all of the time); does not apply responses are set to missing. The individual level scale score is a mean of the responses for items within the scale. The mean is used instead of a summed scale to take into account the valid option of does not apply. If half or more of the responses within a scale are missing, the case is to be deleted. The mean of the items is multiplied by 25 to put it on a scale of 0 100%. Time to score. Approximately 10 minutes. Training to score. None needed. Training to interpret. None needed. Norms available. Not available. Psychometric Information Reliability. Internal consistency. Among a patient population Cronbach alphas for each scale were Physical Demands, 0.89; Time Demands, 0.89; Mental-Interpersonal Demands, 0.91; and Output Demands,0.88 (1). For patients with osteoarthritis, alphas were 0.93, 0.95, 0.97 and 0.96, respectively (2). Test-retest. Among specialty clinic patients, twoweek recall intraclass correlation coefficients for the scales were Physical Demands, 0.69; Time Demands, 0.80; Mental-Interpersonal Demands, 0.80; and Output Demands, 0.74 (1) Validity. Content. Three pilot studies were conducted to generate items, dimensions, and response scales (1). The first study was focus groups held with patients with chronic health conditions. In the second study, patients were interviewed to determine how a sample of respondents interpreted and answered the items generated in the focus groups. A third sample was then used to test alternate question formats of potential items. Construct. The responses of specialty clinic patients were compared with those of their coworkers (1). In each scale, scores of the patients were higher (worse) than those of co-workers: Physical Demands, P 0.03; Time Demands, P 0.01; Mental-Interpersonal Demands, P 0.04; Output Demands, P 0.03. The WLQ scores of patients with three health conditions (rheumatoid arthritis, chronic daily headaches, or epilepsy) were compared (adjusted for age and sex) and found to be significantly different: Physical Demands, P 0.001; Time Demands, P 0.007; Mental-Interpersonal Demands, P 0.001; Output Demands, P 0.02 (1). Persons with rheumatoid arthritis were more limited than persons with headaches in physical demands and less limited than persons with headaches on mental-interpersonal demands. In linear regression models, each of the WLQ scales was significantly associated with the Short Form-36 Role/Physical scale (Physical Demands P 0.002, R 2 0.16; Time Demands P 0.002, R 2 0.15; Mental-Interpersonal Demands P 0.004, R 2 0.14; and Output Demands P 0.001, R 2 0.22) (1). The Time Demands (P 0.07, R 0.07); Mental-Interpersonal Demands (P 0.001, R 2 0.15); and Output Demands (P 0.001, R 2 0.17) scales were associated with the Short Form- 36 Role/Emotional scale, while the Physical Demands scale was not (R 2 0.02). In the sample of patients with rheumatoid arthritis, headaches, or epilepsy, work productivity over the past 2 weeks as it related to health problems was assessed separately via two items,
Adult Work Disability S87 i.e., job effectiveness on symptom days and lower production than required due to health (1). The association of each of the WLQ scales with the summed responses to the two productivity items was assessed in linear regression models. The Output Demands scale was the best predictor of productivity loss, followed by the Mental- Interpersonal Demands scale. In testing in a sample of 230 employed persons with osteoarthritis and 37 patients with no chronic health conditions, the WLQ met internal reliability criteria, detected differences between the 2 groups, and correlated significantly with arthritis pain, stiffness, functional limitation and selfreported work productivity (2). Sensitivity/responsiveness to change. Not evaluated. In a study that compared the efficacy of 3 similar drugs (7), the scores of the Time Demands, Mental-Interpersonal Demands, and Output Demands subscales improved after treatment was initiated. The Physical Demands subscale was not used. Comments and Critique The WLQ is a newly developed instrument that has been shown to be reliable and valid for rheumatoid and osteoarthritis samples, as well as samples with other chronic health conditions. It helps fill a gap in measuring work disability by assessing limitation in ability to work in individuals while they are employed. Extensive questionnaire development studies were conducted and excellent psychometric properties have been demonstrated. The WLQ has been and is being used in studies involving persons with different chronic health conditions and has the advantage of possible use to compare the scores of samples with different conditions. The relationship of WLQ scores with the outcome of premature work loss has not been established as yet; however, limitation in ability to work is an important outcome on its own. Note: The direction of responses to the items on the Physical Demands scale is opposite to that of the other scales. This can be confusing to respondents and must be clearly marked. It is suggested that users discuss the matter with Dr. Lerner. References 1. (Original) Lerner D, Amick BC, Rogers WH, Malspeis S, Bungay K, Cynn D. The Work Limitations Questionnaire. Med Care 2001;39:72 85. 2. Lerner D, Reed JI, Massarotti E, Wester LM, Burke TA. The Work Limitations Questionnaire s validity and reliability among patients with osteoarthritis. J Clin Epidemiol 2002;55:197 208. 3. Wolfe F, Flowers N, Urbansky N. The effect of health-related work limitations on the income of employed adults with rheumatoid arthritis (RA) [abstract]. Arthritis Rheum 2001;44 Suppl 9:S152. 4. Allaire SH, Kalish RA, Lerner DJ. Work limitations of employed persons with rheumatoid arthritis (RA) [abstract]. Arthritis Rheum 1998;41 Suppl 9: S223. 5. Wolfe F, Sesti AM. The effect of health-related work limitations on the income of employed adults with fibromyalgia [abstract]. Arthritis Rheum 2001;44 Suppl 9:S67. 6. Amick BC, Lerner D, Rogers WH, Rooney T, Katz JN. Measuring health-related work outcomes in populations with musculoskeletal injuries. Spine 2000;25:3152 60. 7. Kroenke K, West SL, Swindle R, Gilsenan A, Eckert GJ, Dolor R, et al. Similar effectiveness of paroxetine, fluoxetine, and sertraline in primary care: a randomized trial. JAMA 2001;286:947 55. RHEUMATOID ARTHRITIS WORK INSTABILITY SCALE (RA-WIS) General Description Purpose. To screen for work instability, i.e., the consequences of a mismatch between an individual s functional ability and his/her work tasks that places the individual at risk for work disability (lowered productivity/ premature job loss, etc.) (1). Content. Disease symptoms on the job, thoughts and feelings about work, work adaptations. Developer/contact information. Gil Gilworth, Research Physiotherapist, Academic Unit of Musculoskeletal and Rehabilitation Medicine, University of Leeds, 36 Clarendon Road, Leeds LS2 9NZ UK. E-mail: gilworths@aol.com. Versions. English, United Kingdom. Number of items in scale. There are 23 items. Subscales. None. Populations. Developmental/target. Employed persons with rheumatoid arthritis. Other uses. None. WHO ICF Components. Activity limitation; Participation restriction.
S88 Allaire Administration Method. Self-report questionnaire. Training. None required. Time to administer/complete. 5 minutes or less. Equipment needed. No special equipment needed. Cost/availability. Registration is required to use the instrument; contact Gil Gilworth. Freely available for clinical use; charges may be applicable for commercial trials. Scoring Responses. Scale. Yes/No response format. Score range. The range is 0 23. Interpretation of scores. Score 10 low work disability risk; vocational intervention (e.g., job accommodation such as modification to workplace practices, alternative equipment), change in job, etc.) usually not needed. Score 10 to 17 medium work disability risk; vocational intervention often needed, and score 17 high work disability risk; vocational intervention almost always needed. Method of scoring. Count total number of yes responses. Time to score. 5 minutes or less. Training to score. None needed; guidance notes are available with registration. Training to interpret. None needed. Norms available. Not available at this time. Psychometric Information Reliability. Test-retest. Examination of responses of 51 employed subjects to identical questionnaires sent 2 weeks apart; Spearman s rho correlation 0.89. Validity. Content. There were 76 potential question items generated through interviews with 45 employed subjects with rheumatoid arthritis. Further testing of these 76 items was conducted among 206 employed subjects with rheumatoid arthritis. Construct. To determine which of the 76 items best discriminated across levels of work instability, full vocational assessments were conducted on 31 subjects by 2 physiotherapist/ergonomists who assigned a 0 4 score indicating level of risk for work disability to each of the subjects. The responses of these 31 subjects to the 76 items were then examined to determine which of the items best discriminated across the 5 levels of risk for work disability; 36 such items were identified. The internal construct validity of the 36 items was then assessed by Rasch analysis, using the data from the sample of 206 subjects. The Rasch model identified 23 items on a single construct of work instability that were free from bias for age and sex. Model fit data were item fit, mean 0.56 (SD 0.092), and person fit, mean 0.062 (SD 0.595). An item trait interaction of chi square 34.1 (degrees of freedom 46; P 0.9) indicated invariance for the scale. When the scores on the 23 items from the 31 subjects assessed by the physiotherapist/ergonomists were examined, it was determined that a score of 10 or higher identified 82% of those needing vocational intervention, while 95% of those with a score of 17 or higher needed vocational intervention. Sensitivity/responsiveness to change. Not assessed yet. Comments and Critique The WIS is a newly developed instrument that is beginning to be used in rheumatoid arthritis samples. It helps fill the gap in measuring risk of work disability in individuals while they are employed. Questionnaire items were generated by employed persons with rheumatoid arthritis. The discriminatory properties of the items were corroborated by physiotherapist/ergonomist experts. The scaling properties of the instrument have been well demonstrated. The WIS has the advantage of evaluating the impact of rheumatoid arthritis specifically. The relationship of WIS scores with the outcome of work disability has not been established as yet, however, work instability is an important outcome on its own. The established cutoff scores help clinicians determine which patients need referral for further vocational assessment or rehabilitation services. Note: The wording of a few questionnaire items may need to be changed for use in the US. Reference 1. (Original) Gilworth G, Chamberlain MA, Harvey A, Woodhouse A, Smith J, Smyth MG, et al. Development of a work instability scale for rheumatoid arthritis. Arthritis (Rheum) Arthritis Care Res 2003;49:349 54.
Adult Work Disability S89 Measure/Scale Content Measure outputs Work Instability Scale (WIS) Effects of rheumatoid arthritis at work One overall score (0 23) is obtained. Work Limitations Questionnaire (WLQ) Limitations in performing work demands 4 scores are obtained, one for each of the Physical, Time, Mentalinterpersonal, and Output Demand subscales. Scores for each subscale range from 0% to 100%. *RA rheumatoid arthritis; OA osteoarthritis. Summary Table of Work Disability Measures* No. of items Response format Method of administration Time for administration Validated Population Psychometric properties Reliability Validity Responsiveness 23 Yes/no Self-report 5 minutes RA Test-retest: excellent 25 5-point ordinal scale; direction of responses to one set of items is opposite that of the other sets; Does not apply response also available Self-report 10 minutes OA, RA, fibromyalgia, low back pain, and other chronic conditions Internal consistency: excellent; test-retest: good; (ref. 1) internal consistency excellent to good in OA sample (ref. 2) Content and Construct: Good-limited testing, but clinically based Content and Construct (known group and convergent): excellent; (ref. 1) excellent validity in an OA sample (ref. 2) Not tested Not formally tested; in a study comparing the impact of 3 drugs, scores of the WLQ scales used (all except Physical) improved post treatment (ref. 3)