Hypertension, microalbuminuria and renal dysfunction: the Renal Dysfunction in Hypertension (REDHY) study

AIMS: We assessed the prevalence of kidney dysfunction evaluated by different methods to estimate glomerular filtration rate (GFR) in a wide group of nondiabetic hypertensive patients, without cardiovascular (CV) complications and without known renal disease, participating in the Renal Dysfunction in Hypertension (REDHY) study. METHODS: A total of 1,856 hypertensive individuals (mean age 47 +/- 14 years; men 53%), free from diabetes mellitus and CV complications, and consecutively attending our outpatient hypertension center, were enrolled. Patients with a body mass index >35 (calculated as kg/m(2)) were excluded. The GFR was estimated by the creatinine clearance rate (CrCl), the simplified Modification of Diet in Renal Disease Study prediction equation (MDRD), the Cockcroft-Gault formula (CG) and the Mayo Clinic quadratic equation (Mayo). A 24-hour urine sample was collected to evaluate CrCl and albumin excretion rate (AER). Albuminuria was defined as an AER greater than 20 microg/min. RESULTS: The prevalence of albuminuria was 23.4% (22.7% microalbuminuria and 0.7% macroalbuminuria). Mild renal dysfunction (defined as 24-hour AER >20 microg/min in presence of eGFR > or =60 ml/min per 1.73 m(2)) was found in a proportion of patients ranging from 20.3% using CrCl, to 18.4% using the MDRD equation. The prevalence of overt renal insufficiency (estimated GFR <60 ml/min per 1.73 m(2)) was higher when CrCl (10.8%) or the MDRD equation (10%) was used to estimate the GFR, instead of the CG (7.4%) or Mayo equation (5.4%) (p<0.0001). CONCLUSIONS: Mild renal dysfunction and overt renal insufficiency are highly prevalent among subjects with nonmalignant arterial hypertension without CV complications. However, the prevalence of moderate-to-severe renal function impairment is strongly influenced by the method used to estimate the GFR.