Validation of diagnostic coding for chronic kidney disease using a Japanese hospital-based database

The validity of the International Classification of Diseases 10th Revision (ICD-10) codes for chronic kidney disease (CKD) in Japan have not been evaluated. In this study we evaluated the validity of CKD-related ICD-10 codes in Japan.

This retrospective cohort study used the JMDC hospital-based database, which comprises claims and laboratory data from over 1,000 medical institutions in Japan. Patients who underwent two serum creatinine measurements between April 2014 and August 2022 were identified; the second measurement was obtained 90–365 days after the first. The estimated glomerular filtration rate (eGFR) was calculated. CKD was defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria: an eGFR < 60 mL/min/1.73 m² for both measurements. Markers of kidney damage such as albuminuria were unavailable. Patients assigned CKD-related ICD-10 codes (N183, N184, N185, N189, N19, E102, E112, E142, and I120) within 365 days of the initial serum creatinine measurement were identified. Subsequently, the positive predictive value (PPV), sensitivity, specificity, and negative predictive value (NPV) were calculated.

Among the 618,208 included patients, 59,139 were assigned CKD-related ICD-10 codes and 172,657 met the KDIGO criteria. The overall PPV, sensitivity, specificity, and NPV were 57.9%, 19.8%, 94.4%, and 75.2%, respectively. In contrast, the PPVs of N183, N184, N185, and N189 exceeded 80%.

In Japan, the PPV of the ICD-10 codes for CKD was 57.9%, marginally lower than values reported in the United States (86.1%) and Canada (60.1%). Several ICD-10 codes may be useful for identifying patients with CKD, despite their limited sensitivity.