Radiation exposure from diagnostic imaging: agreement between self-report and medical records

Data on diagnostic imaging procedures from a highly structured interview were compared to medical records in a case-control study of radiography and acute myelogenous leukemia. Three hundred and twenty-eight cases and 315 controls (78% of participants) had medical records available from an average of 71% of providers. Proxies were used for 49% of cases because of rapid fatality. Mean agreement (number of procedures in medical records subtracted from number in interview) showed similar levels of overreporting in cases [0.6; 95% confidence interval (CI): 0.0, 1.1] and controls (0.7; CI: 0.2, 1.3) with few procedures (<= 10). Most participants with more procedures underreported exposure, and underreporting increased with increasing exposure, especially among cases [mean (CI) agreement = -2.1 (-4.3, 0.0) for 11-20 procedures, -6.4 (-13.6, 0.7) for >20 procedures] and case proxies. High-dose, fluoroscopic, and non-routine procedures were self-reported more accurately than low-dose, non-fluoroscopic, and routine procedures, respectively (p < 0.01 for each comparison), and tended to be underreported. Case-control differences in agreement were non-significant for these categories of procedures. We conclude that diagnostic imaging procedures of most interest to the AML-radiography hypothesis are self-reported accurately but that underreporting does occur and might lead to attenuated risk estimates.