The Incidence of Imprecise ICD-10 Coding in Patients with Cutaneous T-cell Lymphoma: A MarketScan Database Study

Background: The term “Primary Cutaneous T-cell Lymphoma” (primary CTCL), although used largely interchangeably with mycosis fungoides in the past, actually represents numerous non-Hodgkin lymphomas with highly variable and distinct characteristics. Accuracy of claims-based research studies of CTCL hinge on the precision of ICD-10 coding, but the incidence of imprecise coding for CTCL has not been extensively studied. Objective: To determine the incidence of imprecise ICD-10 coding in CTCL patients in a large, commercial claims database. Methods: We analyzed the Marketscan database from October 1, 2015 to December 31, 2018 to determine the proportion of patients designated only with the generic CTCL code in the absence of a code for a more specific diagnosis. Results: Of 3,953 patients meeting the criteria for inclusion, only 107 (2.7%) had a generic CTCL code without a more specific diagnosis code. Conclusions: These results suggest that the majority of CTCL claims are precisely coded, although until future studies investigate the accuracy of diagnosis, the results of claims-based studies in the realm of CTCL should be interpreted with caution.