Choice of time for urine collection for detecting early kidney abnormalities in hypertensives

The aim of this study was to determine the most appropriate urine collection for detecting differences in the excretion rates of albumin, gamma glutamyl transpeptidase (GGT) and N-acetyl-beta-D-glucosaminidase (NAGA) between normotensive subjects and hypertensive patients on treatment. Twenty treated hypertensive patients, mean (SEM, standard error of mean) age; 52.2 (6.2) years and 20 normotensive subjects, mean age 49.2 (4.2) years, were studied in a consecutive sampling design. Urinary excretion rates of albumin, GGT and NAGA were determined in consecutive timed urine samples collected overnight and during 3-5 h the next morning. Mean (SEM) overnight excretion rates for albumin, GGT and NAGA for normotensive subjects were 11.05 (1.18) micrograms/min, 17.00 (2.20) mU/min and 6.55 (0.39) mU/min, respectively, which were significantly lower than those of hypertensive subjects which were 20.77 (2.14) micrograms/min, 21.84 (1.65) mU/min and 10.92 (0.87) mU/min, respectively (P < 0.05). The mean (SEM) percentage increases in urinary albumin, GGT and NAGA in morning urine collections of normotensive subjects of 15.22 (3.88)%, 34.04 (6.45)% and 11.54 (3.63)%, respectively were significantly lower than 107.03 (15.04)%, 121.96 (16.71)% and 72.75 (7.50)% found in hypertensive patients (P < 0.05). These data suggest that were urinary albumin and tubular enzyme excretion to be used as correlates of hypertensive renal damage, ambulatory urine collections may be more sensitive than overnight collections.