Predictive Value of the International Classification of Diseases, 9th Revision Codes for Identifying Ocular Oncology Diagnoses

Introduction: To determine the predictive value of International Classification of Diseases, 9th Revision (ICD-9) billing codes for identifying ocular oncology diagnoses. Methods: Population-based retrospective cohort study of all Olmsted County, Minnesota residents with any ocular neoplasm-related ICD-9 code from January 1, 2006 to October 1, 2015. All medical records were reviewed for confirmation of ocular neoplasm. Diagnoses with ≥5 cases confirmed via medical record review were compared to corresponding ICD-9 codes. Main outcome measures included positive predictive value (PPV), negative predictive value (NPV), sensitivity, and specificity of ICD-9 codes. Results: Among 3,932 subjects with ≥1 ocular neoplasm-related ICD-9 code, 21 diagnoses met study criteria. The most frequent intraocular, extraocular/orbital, and ocular surface diagnoses were choroidal nevus (n=824), epidermal inclusion cyst (n=263), and conjunctival nevus (n=74), respectively. PPVs ranged from 1.2% to 73.8%, NPVs from 96.9% to 100%, sensitivity from 0% to 100%, and specificity from 85.7% to 100%. Among malignant neoplasms, PPV ranged from 0% to 73.8%: ocular surface squamous neoplasia (PPV: 0%), choroidal melanoma (PPV: 25.0%), eyelid squamous cell carcinoma (PPV: 46.7%), and eyelid basal cell carcinoma (PPV: 73.8%). Among benign neoplasms, PPV ranged from 1.2% (dermoid cyst) to 61.6% (choroidal nevus). Conclusion: There was wide variation in predictive value of ocular neoplasm-related ICD-9 billing codes, which suggests that ocular oncology-related claims data alone may overestimate the true number of ocular oncology diagnoses.