A review of self-report instruments measuring health-related work productivity: a patient-reported outcomes perspective.

Health impairment often leads to work impairment in the form of both absenteeism and presenteeism (i.e. reduced productivity while at work). Several self-report productivity instruments have been designed over the past few years to measure the impact of illness on productivity at work and/or in non-work activities. In a review of the literature we identified six generic subjective instruments - the Endicott Work Productivity Scale, Health and Labor Questionnaire, Health and Work Questionnaire, Health and Work Performance Questionnaire, Work Limitations Questionnaire (WLQ) and the Work Productivity and Activity Impairment Questionnaire (WPAI) - that could theoretically be used in any working population. These instruments were usually validated against other subjective measures (such as health-related QOL). Each productivity instrument has benefits in certain research settings, but the psychometric properties of the WPAI have been assessed most extensively. It was the most frequently used instrument and has also been modified to measure productivity reductions associated with specific diseases (e.g. allergic rhinitis, gastro-oesophageal reflux disease, chronic hand dermatitis). The WLQ has also been tested extensively to measure the general health impact and impact of specific conditions. Two migraine-specific subjective instruments were also identified: the Migraine Disability Assessment questionnaire and the Migraine Work and Productivity Loss Questionnaire, of which the latter was found to have better psychometric properties. Productivity outcomes are useful in that they characterise the impact of an illness in the workplace and show the effect of treatment on productivity. Evidence of psychometric properties and generalisability of different instruments was found to a varying degree. Thus, further research is needed to assess the accuracy and usefulness of individual instruments in certain research settings. Health-related productivity has been increasingly recognised as an important component of the burden of illness associated with a given disease; without it, one cannot reliably assess this burden.