[Serum creatinine and creatinine clearance to estimate renal function in essential hypertension]

The shortcoming of serum creatinine (SCr) as an index of renal function is well known, patients can have significantly decreased glomerular filtration rates (GFR) with normal range SCr values, making the recognition of renal dysfunction more difficult. This study was designed to estimate renal function and the prevalence of renal dysfunction in essential hypertensive patients, comparing SCr and 4 formulas used to measure the creatinine clearance (CrCl) (the urinary CrCl formula, Cockcroft-Gault, MDRD and body surface formula) The study included 721 essential hypertensive patients, 319 men (44.2%), 402 women (55.8%), mean age 56.3 +/- 13.9 (53.7 +/- 14.4 vs 58.3 +/- 13.3). In all subjects SCr was measured and 24-h urine sample was collected to evaluate CrCl. Creatinine clereance was calculated by 4 formulas. Patients were grouped according to age (< 40, 41-65, 65-75 and > 76) and renal function was classified as normal when SCr < 1.4 in women and 1.5 mg/dl in men and CrCl (> 60 ml/m, respectively) within the above written formulas. SCr increases with age (1.01 +/- 0.36 vs 1.3 +/- 1.15) and CrCl decreases according to the 4 formulas (107.6; 92.8; 74.7 and 57.3 for the urinary SCr formula); (117.7; 87.7; 65.9 and 49.5 for the CC formula); (87.4, 74.9, 66.5 and 61 for the MDRD formula) and (97, 85.3, 71.9 and 57.3 for the body suface formula). The 4 formulas are comparable markers of renal function in the overall population. With any formula the percentage of patients with impaired renal function was much higher than indicated by the plasma creatinine alone (4% for SCr) vs 18.3-25.3% (CrCl < 60 ml/m) according to the 4 formulas. This study documents the substantial prevalence of abnormal renal function in essential hypertension. Estimation of GFR may help to facilitate the early identification of patients with renal impairment.