Accuracy of basic cancer patient data: results from an extensive recoding survey.

The accuracy of data coded from the medical records of 985 patients from 22 major U.S. cancer centers was checked by recoding during 1978-81. The 29 items covered demographics, diagnosis, and therapy. Original codes were compared to recodes, and disagreements were classified as major or minor. The highest rate of major disagreements, 23%, was for stage of disease, followed by 10% for histology and 7% for site. Major disagreement rates for most other items were under 7%. Only 3% of a large sample of major disagreements involved justifiable differences in interpretation; the others were due to errors in the use of records. Major disagreement rates varied by a factor of 10 across sites, 4 across centers, and 2 across stage of disease. For several items the code "unknown" was overused and led to disagreements. A new procedure is presented for analysis of disagreement rates. The results from this procedure can guide training effort to improve coding accuracy.