Accuracy of colorectal cancer ICD-9-CM codes in Italian administrative healthcare databases: a cross-sectional diagnostic study

Objectives To assess the accuracy of International Classification of Diseases, Ninth Revision - Clinical Modification (ICD-9-CM) codes in identifying subjects with colorectal cancer. Design A diagnostic accuracy study comparing ICD-9-CM codes (index test) for colorectal cancers with medical chart (as a reference standard). Case ascertainment based on neoplastic lesion(s) within the colon/rectum and histological documentation from a primary or metastatic site positive for colorectal cancer. Setting Administrative databases from the Umbria region, Azienda Sanitaria Locale (ASL) Napoli 3 Sud (NA) region and Friuli Venezia Giulia (FVG) region. Participants We randomly selected 130 incident patients from each hospital discharge database, admitted between 2012 and 2014, having colorectal cancer ICD-9 codes located in primary position, and 94 non-cases, that is, patients having a diagnosis of cancer (ICD-9 140-239) other than colorectal cancer in primary position. Outcome measures Sensitivity, specificity and predictive values for 153.x code (colon cancer) and for 154.x code (rectal cancer). Results The positive predictive value (PPV) for colon cancer diagnoses was 80% for Umbria (95%CI 73% to 87%), 81% for NA (95%CI 73% to 88%) and 80% for FVG (95%CI 72% to 87%). The sensitivity ranged from 98% to 99%, while the specificity ranged from 78% to 80% in the three units. For rectal cancer, the PPV was 84% for Umbria (95%CI 77% to 90%), 80% for NA (95%CI 72% to 87%) and 81% for FVG (95%CI 73% to 87%). The sensitivities ranged from 98% to 100%, while the specificity estimates from 79% to 82%. Conclusions Administrative databases in Italy can be a valuable tool for cancer surveillance as well as monitoring geographical and temporal variation of cancer practice.