Comparison of self-reported and register data on sickness absence among Norwegian patients participating in an occupational rehabilitation program
Background: Sick leave and return to work are common outcome variables in studies where the aim is to measure the effect of targeted interventions for individuals that are on sick leave benefits or other allowances. Use of official register data is often restricted, and research on sick leave and return to work are often based on the participants self-reports. However, there is insufficient documentation that there is agreement between self-reports and register data on sick leave benefits and allowances.
Aims: The aim of this study was to analyse the individuals' knowledge about states of sick leave benefits or allowances compared with register data from The Labour and Welfare Administration (NAV) in Norway.
Method: 153 individuals, sick-listed or on allowances, participated in a 4-week inpatient occupational rehabilitation program. 132 (86%) answered a questionnaire on assessments of work, sick leave, and allowances three months after completed rehabilitation. Self-reported data were compared with register data from NAV according to four categories: working, sick-listed, on medical/vocational rehabilitation allowance or disability pension. Agreement between self-reported and register data was evaluated in cross-tabulations and reported with kappa values. Stratified analyses were done for gender, age, education, medical diagnosis and length of sick leave/allowances at baseline.
Results: Good agreement was found for medical/vocational rehabilitation allowance (kappa=.70) and disability pension (kappa=.65). Moderate agreement was found for working (kappa=.49) and fair agreement for sick-listed (kappa=.36). Stratified analyses showed significant better kappa values for individuals that had been sick-listed less than 12 months before entering the rehabilitation program.
Conclusions: Agreements from good to fair were found between self-reported and official register data on sick leave. However, official register data is preferred in research because this will ensure complete data sets. Data on sick leave and other benefits are not absorbing states, and there are often multiple and recurrent episodes. These data may be hard to obtain from self-reports.
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