Intermethod agreement of self-reports compared to register data collection for return to work and sickness absence: a systematic review and meta-analysis

Objectives: To determine the intermethod agreement of self-reported vs. register data of ‘sickness absence’ (SA) and ‘return to work’ (RTW) outcome measurements. Study Design and Setting: We conducted a systematic review and a meta-analysis of studies reporting mean differences (MDs) and sensitivity and specificity for self-report vs. register data and an inductive analysis of the self-report question formulations. An information specialist searched Medline, Embase, PsycINFO for studies published from inception to November 2022. Screening and data extraction was done by two authors independently. Results: Twenty-three studies were included of which eighteen with an overall high risk of bias. Self-reports had a pooled MD of 1.84 SA days (95% confidence interval [CI] 0.26–3.41, I² 98%, 18 studies, 38,716 participants) compared to registries which varied among studies from 204 more to 17 days less. The median average sick leave in studies in the self-report group was 8 days (interquartile range 4–23 days). Being absent from work measured with self-report had a sensitivity of 0.83 (0.76–0.88 95% CI) and a specificity of 0.92 (0.88–0.94 95% CI) compared to registry data. The high heterogeneity amongst the studies could not be explained by recall time, gender, register type, prospective or retrospective self-reports, health problem, SA at baseline or risk of bias. Studies lacked standard outcome reporting, had unclearly formulated questions in self-reports and there was little information on the registers’ quality. Conclusion: Current self-reports may differ from register-based absence data but in an inconsistent way. Due to inconsistency and high risk of bias the evidence is judged to be of very low certainty. Further research is needed to develop clear standard questions which can be used for SA and RTW self-reports. Quality of registers needs to be better evaluated. Percentage positive and negative agreement, MDs and 2 × 2 tables should be reported for studies investigating agreement between SA and RTW outcome measures.