Role of hospital claims databases from care units for estimating thyroid cancer incidence in the Rhone-Alpes region of France

Background: Incidence measures are essentially based on the data collected by cancer registries. Hospital claims databases from care units (PMSI) can be used as a source of information for registries because they contain standard records of most cancer patients. Regarding thyroid cancer, we have evaluated the PMSI as a source of information for the Rhone-Alpes thyroid cancer registry and usefulness of PMSI as a tool for surveillance of thyroid cancer incidence. Methods: Patients with incident thyroid cancer in 2002 were identified in the claims data of the Rhone-Alpes region using an algorithm based on DRG codes of thyroidectomy and on diagnosis codes of thyroid cancer in a principal or secondary position. The patients identified were compared to those in thyroid cancer registry of the Rhone-Alpes region regarding sex, age, zip code of residence, month of discharge and length of stay versus the diagnosis date. When the percentage of cases of claims data identified in the cancer registry and the percentage of cases of the cancer registry identified in claims data were obtained, the capture-recapture method was applied to estimate the number of missing cases and the total number of incident thyroid cancers in the region. Results: 667 patients were identified in claims data while the cancer registry included 677 patients. 95.2% of patients identified in claims data were in the cancer registry and 82.3% of patients in the cancer registry were identified in claims data. Cases lacking in claims data mostly corresponded to micro-cancers which represented 41% of cases in the cancer registry. Regarding cancer above 1 cm, 92% of the cancer registry cases were identified in claims data. Sensitivity of combining information from cancer registry and claims data was 99.2%. Cases lacking in cancer registry, present in claims data base and considered as true cases after obtaining pathological confirmation represented 2% of the whole thyroid cancer population. Conclusion: Claims data obtained from anonymous regional or national bases can be helpful for checking the completeness of thyroid cancer registries and to provide a small amount of unknown cases. They can be considered an acceptable tool for surveillance of thyroid cancer incidence. The significance of the variations in incidence that could be observed from claims data remains to be evaluated in comparison with comparable data obtained from registries.