Reference intervals for serum creatinine for healthy adults in central Africa: a post-hoc analysis

Abstract

Despite current interest in creatinine-based equations for estimating glomerular filtration rate, the evaluation of creatinine reference intervals remains relevant. The present study aimed to establish such reference intervals from a healthy Congolese adult population and to investigate the determinants of serum creatinine. This study was based on post-hoc data of previous epidemiology studies conducted in the general population of Kinshasa. Serum Creatinine measurement was performed with the Roche Cobas (Roche Diagnostics, Mannheim, Germany) enzymatic method calibrated to Isotope Dilution Mass Spectrometry (IDMS) traceable. The creatinine values being not normally distributed, the median values and interquartile range and the 2.5th and 97.5th percentiles were considered. Serum creatinine determinants were investigated by a generalized linear model (GLM). A value of p < 0.05 was the threshold of statistical significance. Of 2,504 Congolese adults screened, 506 (males, 67.7%) were healthy and were involved in this study. Their mean body surface area (BSA) was 1.64 ± 0.15 m2. In males, the median of creatinine was 0.96 [0.87; 1.05] mg/dl and percentiles 2.5th and 97.5th were 0.65 and 1.22 mg/dL, respectively. The reference intervals were between 0.65 (90% confidence interval (CI): 0.63 to 0.67) and 1.22 (90% CI: 1.20 to 1.24) mg/dL for the lower limits (LL) and the upper limits (UL), respectively. In females, the median of creatinine was 0.72 [0.66; 0.80] mg/dl and percentiles 2.5th and 97.5th were 0.50 and 0.95 mg/dL, respectively. The reference intervals were between 0.50 (90%CI: 0.47 to 0.52) and 0.95 (90% CI: 0.93 to 0.98) mg/dL for the lower and the upper limits respectively. The factors independently associated with serum creatinine were age, female gender, the interaction between age and gender, weight, arm circumference, education level, and weekly walking frequency. The reference intervals for serum creatinine for Congolese adults seem close to those of White Europeans, with slightly higher values in Congolese compared to Caucasians, but lower than those of the African-Americans. Constitutional factors and lifestyle impact serum creatinine levels.