Coding patterns among ophthalmologists for hydroxychloroquine retinal toxicity

Abstract

Purpose : Clinical studies increasingly rely on data extraction from electronic medical record’s diagnosis and billing codes; however, coding patterns are not always uniform. This study characterizes International Classification of Disease-9 (ICD-9) coding patterns for hydroxychloroquine (HCQ) retinal toxicity.

Methods : Patients dispensed hydroxychloroquine between 2001-2014 and enrolled in the Kaiser Permanente Southern California plan were examined in this study. Patients’ medical charts were electronically searched for the following ICD-9 codes which connote retinopathy: toxic maculopathy, non-exudative age-related macular degeneration (AMD), drusen (degenerative), and/or (other) background retinopathy. The charts of patients with these codes were then manually reviewed to determine which codes had been used by their ophthalmologists in patients diagnosed with HCQ toxicity.

Results : 23,362 patients were dispensed HCQ between 2001-2014, of which 678 (2.9%) patients received at least one of the above ICD-9 codes. Forty-three patients received a diagnosis code for toxic maculopathy and of these 35 (81.4%) had confirmed HCQ toxicity. There was a total of 52 patients who were diagnosed with HCQ toxicity by their ophthalmologists; however, 32.7% of these patients received a code other than toxic maculopathy in their chart to connote the presence of their HCQ toxicity.

Conclusions : Although toxic maculopathy is the most commonly used ICD-9 code to identify patients with HCQ toxicity, a significant number of patients with toxic maculopathy received other codes in their medical records from their ophthalmologists at the time of toxicity diagnosis. Additionally, almost a fifth of patients who were coded as having toxic maculopathy at some point in their care were ultimately not diagnosed with HCQ toxicity. This study underscores the often imprecise nature of ICD coding which is an important consideration in data extraction for studies. Manual data review is necessary to determine the precise incidence of HCQ toxicity. Unfortunately, ICD-10 does not provide improved specificity for HCQ toxicity. Efforts should be made to create more uniform coding standards among ophthalmologists, especially for rare conditions, and develop more specific future ICD classifications.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.