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Selection bias due to non-response in a health survey among patients with rheumatoid arthritis.

BACKGROUND
Non-response may lead to bias in health(care) outcomes.


METHODS
We compared respondents (n = 334) to a questionnaire survey among patients with rheumatoid arthritis with non-respondents (n = 68) and determined predictors of (non-)response. The bias in prevalence estimates of health characteristics and health care use was quantified.


RESULTS
Self-reported pain and health care utilization were the most important predictors of (non-)response with respondents experiencing pain more often and more often using specific health care services. Bias concerned especially an underestimation of 'never having pain' (60%) and 'no contact with health care services' (51%).


CONCLUSION
More insight into the phenomenon of non-response is important to assess disease burden and health care burden more precisely.