The impact of glaucoma coding in a large claims database.

Purpose: Coding variation and its impact on identified populations is a major concern in database analyses. We assessed potential differences in demographics and healthcare charges among patients with open-angle glaucoma identified through different International Classification of Diseases, Ninth Revision (ICD-9) coding algorithms.
Design: Retrospective database analysis.
Methods: Three glaucoma cohorts were identified based on hierarchical inclusion of patients with >/=2 glaucoma ICD-9 codes (PharMetrics, Inc, Watertown, Massachusetts, USA, 1998 to 2003). Descriptive statistics and healthcare charges were assessed for each cohort.
Results: The three cohorts included 64,380, 14,705, and 4,225 unique patients each. Although significant differences in age, gender, region, payer type, product type, and medical comorbidities existed among the three cohorts, these differences had little impact on resource consumption when the cohorts were combined, given the smaller number of patients outside of the primary cohort.
Conclusions: Glaucoma coding variation in administrative data sets has limited impact on analyses of resource consumption among open-angle glaucoma patients.