When International Classification of Disease (ICD) version 9 (ICD-9) transitioned to ICD-10, there was a marked increase in the complexity of ICD codes with potential for improved specificity in clinical database research. The purpose of this study was to characterize the accuracy of coding for stage of diabetic retinopathy (DR) and DR-related complications (including vitreous hemorrhage, retinal detachment, and neovascular glaucoma) during this transition.
Retrospective chart review of 3 time periods corresponding to the use of: ICD-9 (2014-2015), “early” use of ICD-10 (2015-2016), and “late” use of ICD-10 (2018-2019).
Patients 18 years or older with a diagnosis of diabetic retinopathy at a multispecialty academic institution METHODS: Positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity, and kappa (κ) statistics were generated for each diagnosis. Generalized estimating equations (GEE) models were used to assess the significance of the variables.
The main outcome was the proportion of agreement between the ICD code and documented chart standard for stage of DR and DR-related complications.
600 patients were included in the study (average age 61 years, range 25-93). Overall, there was substantial agreement between the ICD codes for stage of DR and documented standard (κ = 0.66). The proportion of ICD codes in agreement with the documented standard diagnosis increased with time: 66.5%, 78.5%, and 83.3% for ICD-9, “early” ICD-10, and “late” ICD-10, respectively. The odds of agreement were 2.67 (95% confidence interval (CI): 1.49 – 4.76, p<0.001) and 3.96 (95%CI: 2.34 – 6.69, p90%). The odds of agreement were 19.70 (95% CI: 11.54 – 33.64, p<0.0001) times greater for proliferative diabetic retinopathy than nonproliferative diabetic retinopathy. Compared to the stage of DR, DR-related diagnoses were overall less accurately coded (κ = 0.61, 0.48, 0.52 for vitreous hemorrhage, retinal detachment, and neovascular glaucoma).
Coding in ICD-10 is more accurate than ICD-9, particularly for proliferative diabetic retinopathy compared to nonproliferative diabetic retinopathy. The increased accuracy emphasizes the potential for ICD-10 coding to be used effectively in database research.

Copyright © 2020. Published by Elsevier Inc.