Correspondence of back pain patients' self-reports of sick leave and Swedish National Insurance Authority register.

While self-reports of sick absenteeism days are often practical for research, it is not clear how accurate these reports are. 192 Swedish participants recorded the number of days they had been off work for all illnesses, as well as for back pain specifically, for each month during the past 6 mo. These data were then compared to records from the National Insurance Authority in Sweden. The similarity between the data sets was very high, with the correspondence for those reporting 0 to 30 days off being 98%. For those with more than 30 days of self-reported sick leave, the correspondence was 81%, but the reason for the discrepancy may have been a lack of clarity in the question. It is concluded that self-reports correspond well with recorded data and that their use in research is justified.