Validation of a large basal cell carcinoma registry

The epidemiological study of basal cell carcinomas (BCCs) is difficult because BCCs lack distinct disease codes and are excluded from most cancer registries.

To develop and validate a large BCC registry based on electronically assigned Systematized Nomenclature of Medicine (SNOMED) codes and text-string searches of electronic pathology reports from Kaiser Permanente Northern California.

Potential BCCs were identified from electronic pathology reports (n=39,026) in 2005 and were reviewed by a dermatologist who assigned case/non-case status (gold-standard). A subset of the records (n=9,428) was independently reviewed by a second dermatologist to ascertain reliability of case assignment. In addition, a subset of excluded electronic pathology reports from 2005 (n=2,700) was reviewed to determine whether inclusion criteria had missed potential BCCs. We calculated the positive predictive value (PPV) of 3 different algorithms for identifying BCCs from electronic pathology data.

BCC-specific SNOMED codes had the highest PPV for identifying BCCs, 0.992 (95 percent CI: 0.991-0.993). Inter-rater reliability for case assignment was high (kappa=0.92, 95 percent CI: 0.91-0.93). Standardized incidence rates were consistent with previously published rates in the United States.

We created and validated a large BCC registry to serve as a unique resource for studying BCCs.