AZUBIKE CHUKWUEMEKA OGUGUA

Glomerular filtration rate (GFR) is the volume of non-protein plasma filtered by the glomeruli per unit of time (average of 125 ml/min/1.73 m2 of body surface area in adults). Age-related physiological changes influence GFR and results in age determined annual rate of Decline (ADARD) of about 1ml/minute/year. The GFR decline varies among populations due to genetic and environmental factors but the extent and pattern of this decline among ethnic black Nigerians had not been characterized. This study evaluated age-determined changes in GFR among adult black Nigerians and compared values in normotensive and hypertensive individuals by using measured creatinine clearance (mCrCl) and GFR estimating equations as Cockroft-Gault equation (CG), modification of diet in renal disease (MDRD) and National Kidney Foundation chronic kidney disease epidemiology collaboration(NKF CKD-EP!). Two hundred and seventy (270) apparently healthy volunteers (18-70 years), were recruited and arranged 30 per grouped (15 males and 15 females) for 9 age groups (18-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-60, 61-65, 66-70 years). Their age, gender, Pulse rates (PR), blood pressure and mean arterial pressure(MAP)were documented. Ten (10) milliliters (ml) of spot urine was obtained for assays of sodium ion and potassium ion by Ion selective electrode. Spectrophotometric methods were used for creatinine (Cr) and albumin (for calculation of mean urine albumin creatinine ratio, mUACR). Ante-cubital venipuncture was done for 10 ml of venous blood (2 ml anti-coagulated and 8ml coagulated for serum extraction). About 4 ml of serum was used for assays of serum Cr and CystatinC (ELISA). Subjects provided 12 hours timed urine for mCrCl in ml/min. The Mean ± Sem of the data were calculated on excel worksheet and further statistics as analysis of variance (ANOVA), Student’s t-Test, regression analysis and graphs were done with SPSS-29. The mean GFR in ml/min/1.73 m2 were; mCrCl (124.86 ± 5.09), CG (85.22 ± 1.69), NKF CKD-EP! Cr (82.95 ± 1.27), NKF CKD-EP! Cystatin C (72.90 ± 3.88), NKFCKD-EP! Cr-cystc (79.62 ± 2.64) and MDRD(93.44 ± 1.01). The ADARD in GFR (inml/min/yr) were significant (P<0.01) for; mCrCl 3.64, CG equation (0.7501), NKF CKD-EP!cr 2021 (0.4398) and MDRD (0.503). Twenty-one percent (21.1%) of the subjects were hypertensive (MAP>100) and 90.5% had mean Urine Albumin Creatinine ratio (mUACR) of 81.12 ± 3.58 (>30 mg/g). The annual rate of increase in UACR was 1.4457 mg/g (P<0.001). The GFR was significantly lower in hypertensive (P<0.05) while UACR was significantly higher in hypertensive (P<0.01). The ADARD in GFR was significant and associated with significant increase in UACR indicating a strong relationship between these CKD. Hypertension and increased mUACR reduced GFR significantly and increased ADARD in GFR. Early on-set of CKD manifested in this population as increase in mUACR before decrease in GFR occurred. Assessment of GFR must include UACR.