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Validity of the work productivity and activity impairment questionnaire - general health version in patients… Zhang, Wei; Bansback, Nick; Boonen, Annelies; Young, Adam; Singh, Amitabh; Anis, Aslam H Sep 22, 2010

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RESEARCH ARTICLE Open AccessValidity of the work productivity and activityimpairment questionnaire - general healthversion in patients with rheumatoid arthritisWei Zhang1,2, Nick Bansback1, Annelies Boonen3, Adam Young4, Amitabh Singh5, Aslam H Anis1,2*AbstractIntroduction: The Work Productivity and Activity Impairment (WPAI) questionnaire is a well validated instrument tomeasure impairments in work and activities. However, its validation among patients with rheumatoid arthritis (RA)has not been well established. The present study’s purpose is to evaluate the construct validity of the WPAI-generalhealth version among RA patients and its ability to differentiate between RA patients with varying health status.Methods: Patients who were enrolled in the Early Rheumatoid Arthritis Network cohort and were employed attheir most recent follow-up were recruited into this sub-study. A questionnaire battery incorporating the WPAI wasadministered along with a number of health outcomes including the Multidimensional Health AssessmentQuestionnaire, fatigue and patient assessment of disease activity. The construct validity of the WPAI was tested bythe correlations between the WPAI and the health outcomes and other measures of productivity. Student’s t testswere used to identify whether the WPAI outcomes differed between the two levels of heath status based on themedian of health outcomes.Results: A total of 150 patients completed the WPAI questionnaire. The average age was 52 years old and thedisease duration was 37.5 months since the first rheumatology visit. Of the 137 patients who were working for pay,26 reported missing work in the past week due to their health problem, accounting for 45.5% of their workingtime (absenteeism). While 123 patients were working, 24% of their work was impaired due to their health problem(presenteeism). In addition, 33% of the patients’ regular daily activities (activity impairment) had been preventeddue to their health problems. There were moderate correlations between the WPAI absenteeism and function,pain, fatigue, and disease severity (r = 0.34 to 0.39). The WPAI presenteeism and activity impairment were stronglycorrelated with the health outcomes (0.67 to 0.77). Patients with more severe disease status (for example, low/highfunctional disability by median) had significantly higher absenteeism (4%/15%), presenteeism (15%/39%), andactivity impairment (19%/53%) than those with less severe disease status.Conclusions: The WPAI is a valid questionnaire for assessing impairments in paid work and activities in RA patientsand for measuring the relative differences between RA patients with different health status.IntroductionRheumatoid arthritis (RA) is the most common form ofinflammatory arthritis with a prevalence rate of about 1%and an annual incidence of 3 per 10,000 adults [1]. Thereis considerable evidence that RA can impact patients’productivity even during the very early phase of the dis-ease. According to Burton et al., the time between RAonset until 50% probability of being permanently workdisabled varied from 4.5 to 22 years [2]. Merkesdal et al.found that within the first three years of RA, there wasan average of 82 days of sick leave per person-year and26% of patients lost work because of RA [3]. Sick leavewas more significant in the first year with an average of113 days. In a study on patients with inflammatory jointconditions present for <12 months, Geuskens et al.found that 26% of all patients and 35% of the patientswith RA reported more than two weeks of sick leave inthe past six months [4]. In terms of the impact of RA on* Correspondence: aslam.anis@ubc.ca1Centre for Health Evaluation and Outcome Sciences, St Paul’s Hospital, 620-1081 Burrard Street, Vancouver, BC V6Z 1Y6, CanadaFull list of author information is available at the end of the articleZhang et al. Arthritis Research & Therapy 2010, 12:R177http://arthritis-research.com/content/12/5/R177© 2010 Zhang et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative CommonsAttribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction inany medium, provided the original work is properly cited.unpaid work, a recent clinical trial showed that at base-line patients with RA reported 9.2 missed days of house-hold work and 11.2 days with productivity less than orequal to 50% in household work in one month [5].Another trial at baseline found that RA patients gotabout 11 hours of unpaid or paid help to take over theirunpaid work [6]. In the literature, functional disabilityhas consistently been found to be associated with workdisability [7-9]. In addition, pain and poor physical func-tioning were also associated with increased sick leave andreduced productivity at work [4,10].In general, the impact of RA on paid work includesemployed people missing time from work (absenteeism),reduced performance while at work (presenteeism),reduced routine working hours through changing or evenlosing jobs (employment status change). The impact onunpaid work usually refers to the impact of health pro-blems on regular daily activities such as household work,shopping, and child care.The Work Productivity and Activity Impairment(WPAI) questionnaire is an instrument to measureimpairments in both paid work and unpaid work [11,12].It measures absenteeism, presenteeism as well as theimpairments in unpaid activity because of health problemduring the past seven days. It has been validated to quan-tify work impairments for numerous diseases such asasthma, psoriasis, irritable bowel syndrome (IBS), anky-losing spondylitis (AS) and Crohn’s disease [12-15].In addition, the WPAI questionnaire has been used tocompare work impairments between treatment groups inclinical (studies and) trials or between subjects with dif-ferent disease severity levels [13-18]. However, the valida-tion of this instrument among patients with RA has notbeen well established.The objective of the study is to evaluate the constructvalidity of the WPAI-general health version (WPAI-GH)among RA patients and its ability to differentiatebetween RA patients with varying health status.Materials and methodsStudy designThis study is a cross-sectional study. Patients wererecruited from a UK based registry of RA, the EarlyRheumatoid Arthritis Network (ERAN), which is a groupof rheumatology centres in the UK and Eire with aninterest in treatment patterns and outcome in patientswith recently diagnosed RA in normal clinical settings.Patients had already consented to take part in the ERANresearch study. Patients who reported they wereemployed at their most recent follow-up with ERANwere invited to participate in this substudy. Those whoagreed were sent a questionnaire battery. The question-naire battery including the WAPI-GH and health out-come measures was administered at one time point. TheWPAI-GH was used to measure the patients’ workimpairments. Ethical approval was gained from WestHerts Multi-centre Research Ethics Committee, UK.WPAI-GH outcomesThe WPAI-GH consists of six questions: 1 = currentlyemployed; 2 = hours missed due to health problems;3 = hours missed other reasons; 4 = hours actuallyworked; 5 = degree health affected productivity whileworking (using a 0 to 10 Visual Analogue Scale (VAS));6 = degree health affected productivity in regular unpaidactivities (VAS) [11,12]. The recall period for the ques-tions 2 to 6 is seven days. Four main outcomes can begenerated from the WPAI-GH and expressed in percen-tages by multiplying the following scores by 100: 1) per-cent work time missed due to health = Q2/(Q2 + Q4)for those who were currently employed; 2) percentimpairment while working due to health = Q5/10 forthose who were currently employed and actually workedin the past seven days; 3) percent overall work impair-ment due to health Q2/(Q2 + Q4) + ((1 - Q2/(Q2 +Q4)) × (Q5/10)) for those who were currently employed;4) percent activity impairment due to health Q6/10 forall respondents [11,12]. For those who missed work anddid not actually work in the past seven days, the percentoverall work impairment due to health will be equal tothe percent work time missed due to health.Construct validity: relation with healthWe selected a number of instruments measuring healthstatus that we believed would be correlated with pro-ductivity outcomes. The Multidimensional HealthAssessment Questionnaire (MDHAQ) is a validatedone-page questionnaire including a measure of func-tional disability, pain, and patient global health estimate[19]. The scoring of the MDHAQ was as follows: a)Function score: 10 activities of daily living (ADL) werescored 0 to 3, 0 = “without any difficulty”, 1 = “withsome difficulty”, 2 = “with much difficulty”, and 3 =“unable to do.” To be consistent with the Health Assess-ment Questionnaire score (HAQ), the sum of 10 ADLscores was divided by 10 to give a score of 0 to 3; b)Pain VAS; c) Patient global estimate VAS on healthimpact. Fatigue VAS was used to measure patientassessment of fatigue problem. Patient global assessment(PtGA) of disease activity was used as a proxy of diseaseactivity. Previous studies have found a strong correlationbetween the patient global assessment of disease activityand the disease activity score including 28-joint counts,with a VAS score greater than 40 indicating high diseaseactivities [20]. All the VAS scales were presented as 21circles to facilitate scoring without a ruler and an arith-metic scale of 0 to 10 in 0.5 unit increments was printedbelow the circles.Zhang et al. Arthritis Research & Therapy 2010, 12:R177http://arthritis-research.com/content/12/5/R177Page 2 of 7Construct validity; relation with other measure ofproductivityQuestions on productivity adapted from alternativequestionnaires were also included to assess the consis-tency of responses. They included the number of absentworkdays in the past three months, a question adaptedfrom the PROductivity and DISease Questionnaire(PRODISQ) [21], and questions adapted from Healthand Labour Questionnaire (HLQ) [22,23] asking aboutlost hours due to presenteeism (the difference betweenthe numbers of hours actually worked in the past sevendays and the estimated number of hours used to com-plete the same work if patients did not experience anyhealth problems) and the impact of health on unpaidwork activities (hours of getting help with unpaid workactivities in the past seven days).In addition, the ability of the WPAI-GH to discrimi-nate between better and worse health states was testedby dividing patients into two groups based on the med-ian of the scores for function, pain, health impact, fati-gue and disease activity (Better status: ≤median; Worsestatus: >median).AnalysisWe measured the extent to which WPAI productivity out-comes were correlated with health status outcomes andthe productivity questions adapted from alternative ques-tionnaires. Due to the skewed nature of the productivityoutcome data, nonparametric correlation (Spearman’s cor-relation coefficient) was used to assess construct validity.For a comparison between two groups, the effect size,the standardized mean difference between two groups ona measured outcome, was calculated for all WPAI-GHoutcomes. An effect size of one indicates a change inmagnitude equivalent to one standard deviation. Accord-ing to Cohen [24,25], the absolute value of effect sizes (d)can be categorized as small (d = 0.2 to 0.5), medium (d =0.5 to 0.8), or large (d > 0.8). A larger effect size indicatesbetter discriminative ability. Student t tests were used toidentify whether WPAI outcomes differed between thetwo levels of heath status. Wilcoxon tests were also useddue to the skewed nature of the productivity outcomedata.ResultsA total of 354 patients believed to be in some sort ofwork in ERAN were contacted for the study and 186(53%) agreed to take part in the study and were sentthe questionnaires. One hundred and fifty-two patientssent back the questionnaire but two of these patientsdid not respond to the questions in the WPAI so thatno WPAI outcomes could be calculated. Therefore, atotal of 150 patients were included in the analysis.Among the 150 patients, the average age was 52 yearsold and 72% were female (Table 1). The sample’s dis-ease duration was 37.5 months since their first rheuma-tology visit. Patients had relatively mild function (0.6),pain (3.6), fatigue (4.6) and disease activity (3.6). Of the137 (91%) patients that were working for pay, 26 (19%)reported missing work (absenteeism) in the past weekdue to their health, accounting for 45.5% of their work-ing time (Table 2). While 123 patients were working,24% of their actual work was impaired due to theirhealth problem (presenteeism) with only 34 (28%)patients reported no such loss. In addition, 33% of thepatients’ regular daily activities had been prevented dueto their health problems.For the correlation analysis between the WPAI pro-ductivity outcomes and the health status outcomes, allthe correlations were in the logical direction and werehighly significant (Table 3). There were moderate corre-lations between percent work time missed due to healthand function, pain, fatigue, health impact, and diseaseseverity (0.34 to 0.39). The other three WPAI outcomeswere strongly correlated with all of the health statusoutcomes (0.67 to 0.77).The number of absent workdays in the past threemonths was about 4.4 (standard deviation (SD): 10.5)days. The number of hours lost due to presenteeism inthe past seven days was 1.4 (2.8) hours. Overall, patientsgot 4.0 (8.3) hours of help with their unpaid work activ-ities in the past seven days. The percent of work timemissed due to health was moderately correlated withnumber of absent workdays in the past three months(r = 0.56). The correlation between impairment whileworking and hours lost due to presenteeism was 0.39and that between activity impairment and hours of get-ting help on unpaid work activities was 0.39.When the patients were divided into two groupsaccording to the median of each health status outcomeTable 1 Demographics and health statusVariables (n = 150) Mean (SD) Median (Q1 to Q3)Age 52.1 (10.0) 52.9 (45.6 to 60.0)Duration since onset ofsymptom (months)48.7 (23.2) 46.0 (33.0 to 60.0)Duration since first clinicvisit (months)37.5 (18.3) 35.7 (23.7 to 50.9)Function (0 to 3) 0.6 (0.5) 0.5 (0.2 to 0.9)Pain (0 to 10) 3.6 (2.5) 3.0 (1.5 to 5.5)Pt global estimate(0 to 10)3.0 (2.4) 2.5 (1.0 to 5.0)Fatigue (0 to 10) 4.6 (2.9) 5.0 (2.0 to 7.0)PtGA (0 to 10) 3.6 (2.6) 3.0 (1.5 to 5.5)n %Female 108 72.0Pt global estimate, patient global estimate on health impact; PtGA, patientglobal assessment of disease activity; Q1, first quartile; Q3, third quartile.Zhang et al. Arthritis Research & Therapy 2010, 12:R177http://arthritis-research.com/content/12/5/R177Page 3 of 7variable, each of WPAI productivity outcomes was sig-nificantly lower among patients with better health statusthan patients with worse health status (Table 4). Forexample, patients with low functional disability (lowerthan median) had a significantly lower percentage ofwork time missed due to health (4 vs. 15), lower percen-tage of impairment while working due to health (15 vs.39), and lower percentage of activity impairment due tohealth (19 vs. 53) than those with high functional dis-ability. According to the effect size, WPAI outcomeshad large discriminative abilities (1.10 to 1.79) exceptthe percent work time missed due to health whichshowed a medium discriminative ability (0.43 to 0.63).The test results from t tests and Wilcoxon tests agreed(only the results of the t tests were reported).DiscussionThis is the first study to examine the construct validityof the WPAI-GH in a relatively large sample of patientswith RA. The results support that the WPAI-GH dis-plays construct validity as measured by moderate tostrong correlations with all health status measures interms of functional disability, pain, fatigue and diseaseactivity (Table 3). As such, it appears that the WPAIproductivity outcomes are assessing constructs that arerelevant and important to patients with RA. However,the WPAI is moderately correlated with other produc-tivity outcomes such as hours lost due to presenteeismand hours of getting help on unpaid work activitiesmeasured using the questions adapted from the HLQ.This may suggest that it measures another aspect of pre-senteeism and unpaid work productivity in comparisonwith the HLQ. In addition, according to the effect sizeanalysis and paired test, the WPAI-GH could discrimi-nate across health status with worse score being asso-ciated with measures indicating worse health statusamong the patients with RA. The results demonstratethe validity of the WPAI-GH is consistent with previousWPAI validation results for other diseases.It is interesting that absenteeism (percent of work timemissed) correlates less with health than presenteeism(impairment while working). This may be because thedecision to stay home depends on more contextual fac-tors than impairments while working that are related tothe diseases; for example, the type of work, the fear to bea burden to colleagues, attitude towards work, conse-quence for income, fear to lose work, and so on. Thissuggests that absenteeism measures another dimensionof the impact of the disease which is not measured byother health outcome instruments. One previous itemresponse theory study in AS showed that work participa-tion did not fit the unidimensionality of all other cate-gories/domains of the International Classification ofFunctioning, Disability and Health that refer to bodyfunctions, body structures, activities and participation[26]. There is also the role of the social security systemthat is expected to influence more absenteeism than pre-senteeism/activity impairment, which makes absenteeismless comparable internationally [27]. However, the highcorrelation between impairment while working/activityTable 2 WPAI outcomesVariables n Mean (SD) Median (Q1 to Q3)Patients working for pay 137Percent work time missed due to health 136 8.7 (25.2) 0 (0 to 0)Percent work time missed due to health (those with missed time >0) 26 45.5 (41.2) 18 (12 to 100)Patients who actually worked in the past seven days 123Percent impairment while working due to health 122 24.0 (22.7) 20 (0 to 40)Percent impairment while working due to health (those with % impairment while working >0) 88 33.3 (20.1) 30 (20 to 50)Percent overall work impairment due to health 135 29.1 (29.8) 20 (0 to 46)All patients 150Percent activity impairment due to health 150 33.3 (27.6) 30 (10 to 60)Percent activity impairment due to health (those with % activity impairment >0) 123 40.7 (25.1) 30 (20 to 60)Q1, first quartile; Q3, third quartile.Table 3 Spearman correlations between WPAI outcomes and health status outcomesFunction Pain Pt global estimate Fatigue PtGAPercent work time missed 0.39 0.36 0.36 0.37 0.34Percent impairment while working 0.69 0.75 0.74 0.67 0.76Percent overall work impairment 0.67 0.73 0.71 0.68 0.73Percent activity impairment 0.73 0.77 0.77 0.68 0.77Pt global estimate, patient global estimate on health impact; PtGA, patient global assessment of disease activity.Zhang et al. Arthritis Research & Therapy 2010, 12:R177http://arthritis-research.com/content/12/5/R177Page 4 of 7impairment and other health outcomes may be partiallyattributable to the fact that they all use the same measur-ing 0 to 10 scale.Among health outcomes, pain and PtGA were morecorrelated with work impairment and activity impair-ment than function and fatigue. In the literature, painwas found to be highly associated with reduced produc-tivity at work [10]. However, no previous studies haveshown that disease activity is highly correlated withwork and activity impairment among people with RA.Further studies are needed to confirm the relationships.There are two aspects of productivity that are impor-tant to measure: first, the work difficulties or workimpairments due to health which influence work relatedquality of life and/or psychosocial impacts such as jobsatisfaction and stress, and second, the actual productiv-ity losses due to health. The WPAI was designed predo-minantly to measure the first aspect but has been used inthe past to measure and value the productivity losses foreconomic evaluations. However, the WPAI does notnecessarily capture sufficient information to comprehen-sively measure actual productivity losses. To do so, itrequires measures of actual lost time estimators as wellas contextual factors such as job type, workplace teamdynamics and compensation mechanism (a manuscriptfrom Zhang et al. - in submission).A total of 186 patients agreed to participate in thestudy but 150 patients completed WPAI questions andwere included in our analysis. To identify whether therewere non-response biases, we compared patient charac-teristics, including age, gender, duration since onset ofsymptom, duration since fist clinic visit, as well as diseaseactivity score, HAQ and PtGA measured in the mostrecent follow-up with ERAN, between the 150 patientswho were included in the analysis and the 36 patientswho were not. No significant differences were found.A limitation of this study is that no independentemployment measure (gold standard) of missed workhours or work impairment while working was used as avalidation criterion. Severens et al. investigated theagreement between registered and reported sick leave[28]. They demonstrated that 95% of the reported daysof sick leave matched registered data perfectly when therecall period was limited to two and four weeks. Thispercentage decreased to 87%, 57%, and 51% for 2, 6,and 12 months, respectively. Reilly et al. assessed theaccuracy of self-reported work hours missed measuredby the WPAI:IBS version using retrospective diaryamong patients with IBS [13]. The high convergence ofthe WPAI:IBS and retrospective diary suggested thatself-reports of percentage work hours missed during thepast week were accurate.In terms of work impairment while at work, presen-teeism, Lerner et al. established the relationship betweentheir Work Limitation Questionnaire and objective workproductivity measures in two types of occupations [29].However, it is quite difficult to measure the relationshipbetween self-reported and objective measures of produc-tivity at work because the objective measures variedwith occupations as well as workplaces and so is therelationship [30]. Zhang et al. have demonstrated thatthe work productivity loss while at work varies widelywith the approach chosen among people with arthritis[31,32]. Future research should focus on assessing therelationship between self report and objective measuresof productivity loss and examining which approach pro-vides more accurate measure of productivity loss.We did not test the reliability of the WPAI-GHamong patients with RA in this study. The test-retestreliability of the WPAI has been well established inpopulations with different diseases [33,34]. We assumedthat this would not be different for the population withTable 4 WPAI outcomes between two patient groups defined by the median for each health status outcomeFunction Pain Pt global estimate Fatigue PtGAPercent work time missed Better 4.2 (19.0)‡ 1.5 (7.2) 2.0 (7.7)† 3.9 (15.8)‡ 1.6 (7.1)Worse 15.5 (31.5) 16.3 (34.0) 15.6 (33.9) 14.5 (32.4) 16.9 (34.6)Effect size 0.46 0.61 0.55 0.43 0.63Percent impairment while working Better 14.5 (18.8) 11.6 (15.0) 10.9 (13.1) 12.8 (16.8) 11.7 (14.3)Worse 39.1 (20.1) 39.6 (21.1) 40.0 (21.7) 38.7 (21.0) 41.2 (21.0)Effect size 1.27 1.56 1.66 1.38 1.69Percent overall work impairment Better 17.6 (24.8) 12.2 (16.7) 11.8 (15.7) 14.8 (22.1) 12.3 (16.1)Worse 46.5 (28.2) 47.4 (30.0) 47.2 (30.3) 46.0 (28.9) 48.9 (30.1)Effect size 1.10 1.46 1.48 1.22 1.55Percent activity impairment Better 19.0 (21.1) 15.7 (17.0) 15.1 (17.0) 19.6 (21.0) 17.5 (19.0)Worse 52.7 (23.3) 51.9 (24.4) 52.0 (23.7) 49.9 (25.6) 51.9 (24.5)Effect size 1.53 1.73 1.79 1.30 1.58Pt global estimate, patient global estimate on health impact; PtGA, patient global assessment of disease activity.If not indicated, t test P values <0.001; †, t test P values <0.01; ‡, t test P values <0.05.Better status, ≤median; Worse status, >median. The median for each health status outcome was shown in Table 1.Zhang et al. Arthritis Research & Therapy 2010, 12:R177http://arthritis-research.com/content/12/5/R177Page 5 of 7RA. The responsiveness of the WPAI-GH amongpatients with RA will be tested in a future study.This is not the first application of WPAI among RApatients. One application of WPAI in RA was a study pub-lished as an abstract at 2008 American College of Rheuma-tology annual scientific meeting [35]. It was used toexplore the impact of health problems on presenteeism inpatients recently diagnosed with RA as compared to ahealthy comparison group. Another application of WPAIwas conducted by the Canadian Arthritis Network workproductivity study, which was to compare different presen-teeism measures among people with arthritis [31,32]. How-ever, in both studies, only the question measuringimpairment while working (question 5 of WPAI) was usedand the main purposes were not to validate the instrument.The WPAI has been used to measure work productivityin other diseases such as asthma, psoriasis, irritable bowelsyndrome (IBS), ankylosing spondylitis (AS) and Crohn’sdisease [13-18]. The mean percent work time missed hasbeen reported to be 5.0 for people with asthma [18], 4.4for people with IBS [13], 9.0 for people with AS [14] and18.3 for people with Crohn’s disease [15], respectively,compared with 8.7 for people with RA in our study popu-lation. The percent impairment while working has beenreported to be 20.0 in asthma, 15.5 in psoriasis [17], 32.4in IBS, 41.7 in AS and 40.5 in Crohn’s disease comparedwith 24.0 in RA from our study. Correspondingly, per-cent activity impairment has been found to be 32.0, 23.7,41.4, 54.9 and 52.0 compared with 33.3 in our study ofRA patients. According to these WPAI outcomes, itshows that RA has a relatively moderate impact on workproductivity compared to other diseases. However, evenfor a certain disease, the WPAI outcomes vary with dif-ferent levels of severity. Given that our RA populationhas early disease and therefore typically mild diseaseseverity, the other disease populations compared mayhave a relatively more severe disease status. Simple com-parisons should be made with caution.ConclusionsConstruct validity and the discriminative ability of theWPAI-GH have been established in this study. Thus,the WPAI-GH is a valid questionnaire for assessingimpairments in paid work and activities in RA patientsand for measuring the relative differences between RApatients with different health status. The WPAI-GH isuseful for measuring productivity outcomes in clinicalpractice. Further studies are needed to validate a toolfor valuing productivity loss in economic analyses.AbbreviationsADL: activities of daily living; AS: ankylosing spondylitis; ERAN: EarlyRheumatoid Arthritis Network; HLQ: Health and Labour Questionnaire; IBS:irritable bowel syndrome; MDHAQ: Multidimensional Health AssessmentQuestionnaire; PRODISQ: PROductivity and DISease Questionnaire; PtGA:Patient Global Assessment; RA: rheumatoid arthritis; VAS: Visual AnalogueScale; WPAI: Work Productivity and Activity Impairment questionnaire; WPAI-GH: WPAI-general health version.AcknowledgementsWZ is a recipient of a Canadian Institutes of Health Research DoctoralResearch Award in the Area of Public Health Research and a CanadianArthritis Network Graduate Award.Author details1Centre for Health Evaluation and Outcome Sciences, St Paul’s Hospital, 620-1081 Burrard Street, Vancouver, BC V6Z 1Y6, Canada. 2School of Populationand Public Health, University of British Columbia, 5804 Fairview Avenue,Vancouver, BC V6T 1Z3, Canada. 3Department of Internal Medicine, Divisionof Rheumatology, University Hospital Maastricht and Caphri ResearchInstitute, P Debyelaan 25, 6229 HX Maastricht, The Netherlands. 4Departmentof Rheumatology, St Albans City Hospital, Waverley Road, St Albans, HertsAL3 5PN, UK. 5Inflammation Market Access, Pfizer, Inc. 500 Arcola Road, DockE-4303 Collegeville, PA 19426, USA.Authors’ contributionsWZ, NB, AY and AHA were involved in the conceptualization, design, dataacquisition and interpretation. AB and AS participated in theconceptualization and data interpretation. WZ performed data analysis anddrafted the manuscript. NB, AB, AY, AS and AHA critically revised themanuscript. All authors read and approved the final manuscript.Competing interestsThis study was funded by Wyeth (now Pfizer). The Arthritis Research Centreof Canada, where AHA is a senior research scientist, has received a researchgrant from Wyeth. ERAN has received funding from Wyeth Pharmaceuticalsand the Healthcare Commission. AS was an employee of Wyeth and ownedits stocks/shares at the time of the study.Received: 1 April 2010 Revised: 3 September 2010Accepted: 22 September 2010 Published: 22 September 2010References1. Gabriel SE: The epidemiology of rheumatoid arthritis. Rheum Dis ClinNorth Am 2001, 27:269-281.2. Burton W, Morrison A, Maclean R, Ruderman E: Systematic review ofstudies of productivity loss due to rheumatoid arthritis. Occup Med(Lond) 2006, 56:18-27.3. Merkesdal S, Ruof J, Schoffski O, Bernitt K, Zeidler H, Mau W: Indirectmedical costs in early rheumatoid arthritis: composition of and changesin indirect costs within the first three years of disease. Arthritis Rheum2001, 44:528-534.4. Geuskens GA, Hazes JM, Barendregt PJ, Burdorf A: Work and sick leaveamong patients with early inflammatory joint conditions. Arthritis Rheum2008, 59:1458-1466.5. Osterhaus JT, Purcaru O, Richard L: Discriminant validity, responsivenessand reliability of the rheumatoid arthritis-specific Work ProductivitySurvey (WPS-RA). Arthritis Res Ther 2009, 11:R73.6. Zhang W, Bansback N, Guh D, Li X, Nosyk B, Marra CA, Anis AH: Short-terminfluence of adalimumab on work productivity outcomes in patientswith rheumatoid arthritis. J Rheumatol 2008, 35:1729-1736.7. de Croon EM, Sluiter JK, Nijssen TF, Dijkmans BA, Lankhorst GJ, Frings-Dresen MH: Predictive factors of work disability in rheumatoid arthritis: asystematic literature review. Ann Rheum Dis 2004, 63:1362-1367.8. Eberhardt K, Larsson BM, Nived K, Lindqvist E: Work disability inrheumatoid arthritis–development over 15 years and evaluation ofpredictive factors over time. J Rheumatol 2007, 34:481-487.9. Kessler RC, Maclean JR, Petukhova M, Sarawate CA, Short L, Li TT, Stang PE:The effects of rheumatoid arthritis on labor force participation, workperformance, and healthcare costs in two workplace samples. J OccupEnviron Med 2008, 50:88-98.10. Geuskens GA, Hazes JM, Barendregt PJ, Burdorf A: Predictors of sick leaveand reduced productivity at work among persons with earlyinflammatory joint conditions. Scand J Work Environ Health 2008,34:420-429.Zhang et al. Arthritis Research & Therapy 2010, 12:R177http://arthritis-research.com/content/12/5/R177Page 6 of 711. Reilly MC, Zbrozek AS, Dukes EM: The validity and reproducibility of awork productivity and activity impairment instrument.Pharmacoeconomics 1993, 4:353-365.12. Reilly Associates Health Outcomes Research. [http://www.reillyassociates.net].13. Reilly MC, Bracco A, Ricci J, Santoro J, Stevens T: The validity and accuracyof the Work Productivity and Activity Impairment questionnaire -Irritable bowel syndrome version (WPAI:IBS). Alimentary Pharmacology andTherapeutics 2004, 20:459-467.14. Reilly MC, Gooch KL, Wong RL, Kupper H, van der Heijde D: Validity,reliability and responsiveness of the Work Productivity and ActivityImpairment Questionnaire in ankylosing spondylitis. Rheumatology(Oxford) 2010, 49:812-819.15. Reilly MC, Gerlier L, Brabant Y, Brown M: Validity, reliability, andresponsiveness of the work productivity and activity impairmentquestionnaire in Crohn’s disease. Clin Ther 2008, 30:393-404.16. Revicki DA, Willian MK, Menter A, Gordon KB, Kimball AB, Leonardi CL,Langley RG, Kimel M, Okun M: Impact of adalimumab treatment onpatient-reported outcomes: results from a Phase III clinical trial inpatients with moderate to severe plaque psoriasis. J Dermatolog Treat2007, 18:341-350.17. Pearce DJ, Singh S, Balkrishnan R, Kulkarni A, Fleischer AB, Feldman SR: Thenegative impact of psoriasis on the workplace. J Dermatolog Treat 2006,17:24-28.18. Chen H, Blanc PD, Hayden ML, Bleecker ER, Chawla A, Lee JH, TENOR StudyGroup: Assessing productivity loss and activity impairment in severe ordifficult-to-treat asthma. Value Health 2008, 11:231-239.19. Pincus T, Swearingen C, Wolfe F: Toward a multidimensional HealthAssessment Questionnaire (MDHAQ): assessment of advanced activitiesof daily living and psychological status in the patient-friendly healthassessment questionnaire format. Arthritis Rheum 1999, 42:2220-2230.20. Kobelt G, Lindgren P, Lindroth Y, Jacobson L, Eberhardt K: Modelling theeffect of function and disease activity on costs and quality of life inrheumatoid arthritis. Rheumatology (Oxford) 2005, 44:1169-1175.21. Koopmanschap MA: PRODISQ: a modular questionnaire on productivityand disease for economic evaluation studies. Expert Rev PharmacoeconOutcomes Res 2005, 5:23-28.22. van Roijen L, Essink-Bot ML, Koopmanschap MA, Bonsel G, Rutten FF: Laborand health status in economic evaluation of health care. The Health andLabor Questionnaire. Int J Technol Assess Health Care 1996, 12:405-415.23. The health and labour questionnaire (manual). [http://publishing.eur.nl/ir/repub/asset/1313/bmgimt20000609160629.pdf].24. Cohen J: A power primer. Psychol Bull 1992, 112:155-159.25. Cohen J: Statistical Power Analysis for the Behavioural Sciences, 2nd edition.Hillsdale, NJ: Lawrence Erlbaum Association; 1988.26. Cieza A, Hilfiker R, Boonen A, van der Heijde D, Braun J, Stucki G: Towardsan ICF-based clinical measure of functioning in people with ankylosingspondylitis: a methodological exploration. Disabil Rehabil 2009,31:528-537.27. Boonen A, van der Heijde D, Landewe R, Spoorenberg A, Schouten H,Rutten-van Molken M, Guillemin F, Dougados M, Mielants H, de Vlam K, vander Tempel H, van der Linden S: Work status and productivity costs dueto ankylosing spondylitis: comparison of three European countries. AnnRheum Dis 2002, 61:429-437.28. Severens JL, Mulder J, Laheij L, Verbeek V: Precision and accuracy inmeasuring absence from work as a basis for calculating productivitycosts in The Netherlands. Social Science and Medicine 2000, 51:243-249.29. Lerner D, Amick BC, Lee JC, Rooney T, Rogers WH, Chang H, Berndt ER:Relationship of employee-reported work limitations to workproductivity. Med Care 2003, 41:649-659.30. Prasad M, Wahlqvist P, Shikiar R, Shih YC: A review of self-reportinstruments measuring health-related work productivity: a patient-reported outcomes perspective. Pharmacoeconomics 2004, 22:225-244.31. Zhang W, Bansback N, Beaton D, Lacaille D, Gignac M, Badley E,Bombardier C, Anis AH: How is reduced performance at work(presenteeism) associated with measures of disease severity in patientswith osteoarthritis (OA) and rheumatoid arthritis (RA)? [abstract]. AnnRheum Dis 2008, 67:583.32. Zhang W, Gignac MA, Beaton D, Tang K, Anis AH, Canadian ArthritisNetwork Work Productivity Group: Productivity loss due to presenteeismamong patients with arthritis: estimates from 4 instruments. J Rheumatol2010, 37:1805-1814.33. Bushnell DM, Reilly MC, Galani C, Martin ML, Ricci JF, Patrick DL,McBurney CR: Validation of electronic data capture of the Irritable BowelSyndrome–Quality of Life Measure, the Work Productivity and ActivityImpairment Questionnaire for Irritable Bowel Syndrome and theEuroQol. Value Health 2006, 9:98-105.34. Ciconelli RM, Soarez PC, Kowalski CC, Ferraz MB: The Brazilian Portugueseversion of the Work Productivity and Activity Impairment: GeneralHealth (WPAI-GH) Questionnaire. Sao Paulo Med J 2006, 124:325-332.35. Braakman-Jansen LM, Taal E, Kuper I, van de Laar MA: Productivity loss atwork in patients with early rheumatoid arthritis [abstract]. AmericanCollege of Rheumatology annual scientific meeting (presentation 1275), 2008.doi:10.1186/ar3141Cite this article as: Zhang et al.: Validity of the work productivity andactivity impairment questionnaire - general health version in patientswith rheumatoid arthritis. Arthritis Research & Therapy 2010 12:R177.Submit your next manuscript to BioMed Centraland take full advantage of: • Convenient online submission• Thorough peer review• No space constraints or color figure charges• Immediate publication on acceptance• Inclusion in PubMed, CAS, Scopus and Google Scholar• Research which is freely available for redistributionSubmit your manuscript at www.biomedcentral.com/submitZhang et al. Arthritis Research & Therapy 2010, 12:R177http://arthritis-research.com/content/12/5/R177Page 7 of 7


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