Cystatin C and creatinine eGFR reference intervals in healthy adults from Cameroon

Several equations are available for estimation of glomerular filtration rates (eGFRs) from serum cystatin C and creatinine, but data on reference intervals from healthy subjects are scarce. Employing nine well-known equations, we calculated eGFRs for healthy Cameroonians, 194 men and 187 women 18-71 years of age. Reference intervals were calculated using conventional techniques. For subjects < 50 years of age the eGFR reference intervals were with CAPA (men; women) 70.1-127.1; 79.9-172.2, with CKD-EPI_{cys 2012} 75.1-131.2; 81.3-135.5, with LM rev 65.4-106.5; 61.4-110.3, with CKD-EPI_{crea 2021} 74.1-127.2; 67.0-129.8, with mean (LM rev, CAPA) 72.2-110.6; 72.8-136.9, with CKD-EPI_{crea, cys 2021} 81.1-126.6; 77.0-135.7, with EKFC_cys 85.5-116.3; 83.3-124.8, with EKFC_crea 69.4-114.2; 62.8-114.3, and with EKFC_{crea, cys} 82.5-114.0: 77.1-116.4 mL/min/1.73 m², respectively. Median eGFR_cys was significantly higher than eGFR_crea irrespective of equations used. The eGFR_cys difference between healthy men and women aged < 50 years may be explained by lower production rates of cystatin C in women. The higher eGFR_cys reference intervals compared to that of eGFR_crea may be caused by increased tubular secretion of creatinine or increased production of cystatin C in the cohorts used for establishing the equations relative the case in healthy subjects. This suggests that the eGFR equations need to be further assessed regarding accuracy to adequately correspond to true GFR.