Validation of self-reported fractures in a follow-up survey of the Japan Multi-Institutional Collaborative Cohort study.

BACKGROUND: This study aimed to validate self-reported fractures in the Japan Multi-Institutional Collaborative Cohort (J-MICC). METHODS: Of the 10,332 participants who were followed up for 10 years, 1,137 individuals with self-reported fractures were included. Among them, 201 individuals were randomly selected, and 192 individuals with available medical records were analyzed. A false-positive fracture was defined as a self-reported fracture without a clinical diagnosis or record. We calculated the positive predictive value (PPV) stratified by the number of years from injury to response. Multivariate logistic regression analysis was used to elucidate the factors influencing false-positive fractures and to calculate the odds ratios (ORs) with 95% confidence intervals (CIs). The dependent variable was false-positive fractures, and the independent variables included factors such as fracture site, age, sex, body mass index, education, multisite fractures, multiple fractures, and number of years from injury to response. RESULTS: The average age at the time of injury was 69.6 years (range, 50-80 years), and 48 individuals (25.0%) were male. Fractures were reported in the spine (41 individuals, 21.4%), upper limbs (57 individuals, 29.7%), lower limbs (71 individuals, 37.0%), and other locations (23 individuals, 11.9%), respectively. The PPV was 85.4% (164/192 individuals; 95% CI, 79.7-89.7) and was >90% if the period from injury to response was within 3 years. False-positive fractures were significantly associated with a period from injury to response >3 years (OR, 3.46; 95% CI, 1.43-8.37). CONCLUSIONS: elf-reported fractures are useful outcomes; however, recall periods >3 years may increase the risk of misclassification.