Quality of prostate cancer data in the cancer registry of Norway.

Completeness of reporting and internal validity of the coding of prostate cancer in the Cancer Registry (CR) in Norway were examined. Data were matched and evaluated against diagnostic indices at eight selected hospitals in the country and against death certificates from Statistics Norway. Validity control was based on detailed re-analysis of an approximately 1% sample of the registered data during the period 1957-1986. The deficiency in reporting of prostate cancer was less than 1%. The grave deficiencies in hospital patient registers were considered to be of non-systematic nature and should, therefore, not impair the reliability of our investigation of incompleteness. The validity control revealed errors in 0.5% of the data elements, or, illustrated differently, 6% of the patient files had an error, of importance or not, in one of the data elements. One false positive registration was found among 298 controlled patient files (0.3%).