12 Microalbuminuria in elderly hypertensives: variability and relation to clinic and ambulatory blood pressure

Abstract

To examine the short-term reproducibility of urinary albumin measurements and the relation of urinary albumin excretion to the clinic and ambulatory blood pressure levels in elderly untreated hypertensive subjects. Outpatient hypertension clinic of a District General Hospital. The within-patient reproducibility of 24-h urinary microalbumin and electrolyte excretion and relation to 24-h and clinic blood pressure levels. Sixty-four untreated elderly hypertensives (mean age 74.7 years, range 64-82) with systolic blood pressure > or = 160 mmHg or diastolic blood pressure > or = 95 mmHg, or both, were recruited from general practitioner clinics and current outpatient attenders. The patients had not received antihypertensive treatment for at least 4 weeks. The clinic and 24-h non-invasive ambulatory blood pressures were recorded with a simultaneous 24-h urine collection for measurement of the urinary albumin and electrolyte excretion. Thirty-seven subjects performed two consecutive 24-h urine collections for an assessment of the short-term reproducibility of the albumin and electrolyte excretion. The coefficient of variation of 24-h urinary albumin excretion was 62%, and for the albumin:creatinine ratio 52%, compared with 19% for sodium and 15% for potassium excretion. The urinary albumin excretion correlated with clinic systolic blood pressure (r = 0.33, P = 0.01) and with 24-h ambulatory systolic (r = 0.48, P < 0.001) and diastolic (r = 0.32, P = 0.01) blood pressure. The subjects with microalbuminuria (24-h urinary albumin excretion in the range 30-300 mg) had higher clinic and ambulatory blood pressures than those with lower levels of albumin excretion. The low day-to-day intrasubject reproducibility in the 24-h urinary albumin excretion considerably reduces the potential value of single collections in the assessment of microalbuminuria in elderly hypertensives. The urinary albumin excretion correlates with the clinic and 24-h ambulatory blood pressures in elderly hypertensives.