Comparison of ICD-10 Diagnoses and Longitudinal Estimated Glomerular Filtration Rate (eGFR) in the Detection of Incident Stage 3 Chronic Kidney Disease (CKD): A Retrospective Comparison Study Using UK Secondary Care Data

OBJECTIVES: It is estimated that over 10% of the UK population have CKD, yet half of cases are likely not recorded in routine care, particularly at earlier stages of the disease. Unrecorded CKD may be identified using longitudinal eGFR measures from electronic healthcare records (EHR), allowing timely clinical intervention. This study aimed to estimate the proportion of CKD patients identifiable only through eGFR, and report differences in demographic characteristics between recorded (with ICD-10 code) and unrecorded CKD patients.

METHODS: This retrospective study used de-identified EHR from UK NHS partners collated as part of the Arcturis UK Dataset. CKD staging was assigned using a combination of ICD-10 coding and laboratory markers. Patients were stratified into two groups: patients with an ICD-10 confirmed stage 3 CKD diagnosis (N18.3), and patients with longitudinal eGFR measures indicative of stage 3 CKD (sustained eGFR between 30-60 mL/min/1.73m2 over 90 days) but without a stage 3+ ICD-10 code. Descriptive characteristics for these subgroups were collected.

RESULTS: From 67,356 renal patients, 21,109 had a stage 3 CKD ICD-10 code, with 14,165 additional stage 3 patients identified using eGFR alone. There were proportionally more male patients in the eGFR group than the ICD-10 group (53.2% vs 45.1%), while age distributions were comparable (mean age 75.9 (SD 13.8) vs 76.6 (SD 13.4)) and predominantly of white ethnicity (77.3% vs 79.9%). The distribution of comorbidity burden skewed slightly higher in the eGFR group, with median Charlson Comorbidity Index of 1 (IQR 0, 3) compared to 1 (IQR 0, 2).

CONCLUSIONS: These results demonstrate that CKD is often poorly recorded in secondary care, and that eGFR measures may identify incident CKD earlier, with opportunities for early identification of progression. Timely detection of stage 3 CKD is pivotal to slowing disease progression, improving patient outcomes, and reducing consequent healthcare resource utilization.