Validation of the International Classification of Disease 10th Revision Codes for Kidney Transplant Rejection and Failure

Background: Clinical research requires that diagnostic codes captured from routinely collected health administrative data accurately identify individuals with a disease. Objective: In this study, we validated the International Classification of Disease 10th Revision (ICD-10) definition for kidney transplant rejection (T86.100) and for kidney transplant failure (T86.101). Design: Retrospective cohort study. Setting: A large, regional transplantation center in Ontario, Canada. Patients: All adult kidney transplant recipients from 2002 to 2018. Measurements: Chart review was undertaken to identify the first occurrence of biopsy-confirmed rejection and graft loss for all participants. For each observation, we determined the first date a single ICD-10 code T86.100 or T86.101 was recorded as a hospital encounter discharge diagnosis. Methods: Using chart review as the gold standard, we determined the sensitivity, specificity, and positive predictive value (PPV) for the ICD-10 codes T86.100 and T86.101. Results: Our study population comprised of 1,258 kidney transplant recipients. The prevalence of rejection and deathcensored graft loss were 15.6 and 9.1%, respectively. For the ICD-10 rejection code (T86.100), sensitivity was 72.9% (95% confidence interval [CI], 66.6-79.2), specificity 97.5% (96.5-98.4), and PPV 83.8% (78.3-89.4). For the ICD-10 graft loss code (T86.101), sensitivity was 21.2% (95% CI, 13.2-29.3), specificity 86.3% (84.3-88.3), and PPV 11.7% (7.0-16.4). Limitations: Single-center study which may limit generalizability of our findings. Conclusions: A single ICD-10 code for kidney transplant rejection (T86.100) was present in 84% of true kidney transplant rejections and is an accurate way of identifying kidney transplant recipients with rejection using administrative health data. The ICD-10 code for graft failure (T86.101) performed poorly and should not be used for administrative health research.