Agreement Between Self-Reported Cancer Diagnoses and Confirmed Cancer Diagnoses in New York City Firefighters and EMS Workers

BACKGROUND: Because of the delay in the availability of cancer diagnoses from state cancer registries, self-reported cancer diagnoses may be valuable in assessing the current cancer burden in many populations. This study evaluates agreement between self-reported cancer diagnoses and state cancer registry-confirmed cancer diagnoses among 21,467 Fire Department of the City of New York firefighters and emergency medical services workers.  It also investigates the association between World Trade Center (WTC)-exposure and other characteristics in relation to accurate reporting of cancer diagnoses.

METHODS: Participants’ self-reported cancer status was captured from questionnaire responses. Confirmed cancer diagnoses were obtained from state cancer registries, which we used as our “gold standard”. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated comparing self-reported cancer diagnoses to confirmed cancer diagnoses. Multivariable logistic regression models were used to assess the association between WTC-exposure and correct self-report of cancer status, false positive cancer reports, and false negative cancer reports.  In addition to state cancer registry data, the FDNY database includes cases reported to FDNY and confirmed using medical records. We conducted a secondary analysis assessing agreement by including cancer cases confirmed using medical records but not reported in matches to state cancer registries as a confirmed cancer. Sensitivity, specificity, PPV, and NPV were calculated using the expanded confirmed cancer definition. 

RESULTS: Sensitivity and specificity for all cancers combined were 90.3% and 98.7%, respectively. Specificities and NPVs remained consistently high in different cancer types, but sensitivities and PPVs varied considerably. Sensitivities ranged from 33.3% for brain/CNS cancer to 100% for esophageal/gastric cancer. PPVs ranged from 16.3% for bone cancer to 94.2% prostate cancer. WTC-exposure was not associated with accurate reporting, but age and smoking status were associated with false positive reports of cancer. In the secondary analysis the sensitivity, specificity and NPV remained similar to the primary analysis, but the PPV increased to 74.9%. Melanoma skin cancer and hematologic cancers had the greatest number of cases confirmed using only medical records. As a result, the PPV was higher than the primary analysis: 34.9% vs 26.3% for melanoma skin cancer and 70.2% vs. 51.1% for hematologic cancers.

CONCLUSIONS: We have shown very high specificities, NPVs, and general concordance between self-reported cancer diagnoses and state cancer registry-confirmed cancer diagnoses. Given the low prevalence of cancer in most populations, self-reported cancer diagnoses may be particularly useful for ruling out cancer cases in a cohort.