Validation of a measure of health-related production loss: construct validity and responsiveness - a cohort study

BACKGROUND The aim of this study is to evaluate the construct validity and responsiveness of a Swedish measure of health-related production loss as well as to investigate if there is a difference in the level of production loss within a population suffering from persistent back/neck pain and CMDs. METHODS The sample was drawn from a study that assessed employees' health and working capacity in 74 health care units before and after intervention. The study included 692 patients who reported working the previous six months at baseline measurement, and who were also asked to answer questions related to health-related production loss. Health-related measures were general health derived from Short Form-12, health-related quality of life derived from EQ-5D, and work ability derived from the Work Ability Index (WAI). Convergent validity and external responsiveness were assessed using Spearman's Rank Correlation Coefficient and a linear regression model, respectively. RESULTS The different measures of health showed a moderate-to-strong correlation with the measure of health-related production loss and fulfilled the criteria for construct validity. Changes in health and work ability led to significant changes in health-related production loss, which demonstrates external responsiveness. This result is valid for both the total population and for the two different subgroups that were evaluated. CONCLUSIONS The present study shows that this measure of health-related production loss is a valid measure for capturing production loss due to illness, and that work ability is more strongly correlated with health-related production loss than people's general health is. The result shows an average of about 50 % reduced production due to illness, with back pain being the most costly.