Age-dependent error in creatinine clearance estimated by Cockcroft–Gault equation for the elderly patients in a Japanese hospital: a cross-sectional study

The aim of this study is to assess the accuracy of creatinine clearance (CCr) calculated by the Cockcroft–Gault (CG) equation for elderly patients in a Japanese hospital. This study was a retrospective chart review of patients aged ≥ 55 years with a CCr measurement by a 24-h urine collection (24-h) prior to general surgery in our hospital between April 2009 and March 2017. In total, 1028 Japanese patients were included (mean age 73.0 ± 8.9 years). The serum creatinine value was 0.82 ± 0.24 mg/dL. The CCr estimated by CG and measured by 24 h was 64.2 ± 20.9 mL/min and 71.5 ± 21.0 mL/min, respectively. The CG CCr was significantly underestimated in patients aged ≥ 65 years, and the discrepancy exhibited an age-dependent character. The error was reached at 21.7 ± 13.2 mL/min in patients aged ≥ 90 years (P < 0.001). The age-dependent errors almost completely disappeared when the modified CG equation was used, in which the term of age in the original CG equation was constantly regarded as 65, if the patient was 65 years or older. Anesthesiologists and intensivists should pay attention to the potential risk of underestimating kidney function when using the CG equation for Japanese elderly patients.