Effect of ICD-9 to ICD-10 Transition on Accuracy of Codes for Stage of Diabetic Retinopathy and Related Complications: Results from the CODER Study

Abstract

Purpose: When the International Classification of Diseases 9th Revision (ICD-9) transitioned to the International Classification of Diseases 10th Revision (ICD-10), there was a marked increase in the complexity of International Classification of Diseases (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.

Design: 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.

Participants: Patients aged 18 years or older with a diagnosis of DR 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 equation (GEE) models were used to assess the significance of the variables.

Main outcome measure: The main outcome was the proportion of agreement between the ICD code and the documented chart standard for stage of DR and DR-related complications.

Results: A total of 600 patients were included in the study (average age, 61 years; range, 25-93 years). Overall, there was substantial agreement between the ICD codes for stage of DR and the 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, P < 0.0001) times greater for "early" and "late" ICD-10 codes compared with ICD-9 codes, respectively. For specific codes, the overall PPV, NPV, sensitivity, and specificity for nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) were excellent (>90%). The odds of agreement were 19.70 (95% CI, 11.54-33.64, P < 0.0001) times greater for PDR than NPDR. Compared with the stage of DR, DR-related diagnoses were overall less accurately coded (κ = 0.61, 0.48, and 0.52 for vitreous hemorrhage, retinal detachment, and neovascular glaucoma, respectively).

Conclusions: Coding in ICD-10 is more accurate than in ICD-9, particularly for PDR compared with NPDR. The increased accuracy emphasizes the potential for ICD-10 coding to be used effectively in database research.

Keywords: ICD-10; ICD-9; coding; diabetic retinopathy.