Validating regional Hospital Information System data through comparison with a local cancer register to identify interval cancers of a breast screening program.

The objective of this study was to evaluate the accuracy of the Hospital Information System (HIS) in monitoring the breast cancer incidence and interval cancers compared with the cancer registry (CR). The HIS data linked with CR and Mammographic Screening Information System data for breast cancer cases diagnosed in the period 1999-2003. The sensitivity and positive predictive value of the HIS data were calculated using the CR as a gold standard. One thousand two hundred and thirty-six breast cancers were registered by the CR and 1028 were reported in the HIS. The sensitivity rate was 83.2% and the positive predictive value was 83.0%; similar results were obtained in the screening target population (50-69 years old). Fifteen invasive breast cancers occurred among screened women identified by HIS (four interval cancers and 11 screen-detected), two were registered as in situ in the CR. The HIS seems to have the potential to identify interval breast cancers, but the low accuracy of information does not permit an exact measure of the incidence.