Macroalbuminuria is a better risk marker than low estimated GFR to identify individuals at risk for accelerated GFR loss in population screening

Abstract

Macroalbuminuria, erythrocyturia, and impaired renal function are strong predictors of poor renal outcome in patients with known renal disease. However, the yield of mass screening for these variables to identify individuals who are at risk for GFR loss is yet unknown in a Western population. With the use of data from the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study, a prospective, population-based cohort study, the cardiovascular and renal prognosis was investigated in patients with classical renal risk markers: Macroalbuminuria (> or =300 mg albumin/24 h urine), erythrocyturia (> or =250 erythrocytes/L, without leukocyturia), and impaired renal function (both 24-h creatinine clearance and Modification of Diet in Renal Disease clearance below the fifth percentile of age- and gender-matched control subjects). The 8592 patients who were included in this study were followed for a 4-yr period. We identified 134 patients with macroalbuminuria, 128 with erythrocyturia, and 103 with impaired renal function. There was only a little overlap among the three groups. The prevalence of macroalbuminuria, erythrocyturia, and impaired renal function was calculated to be in the general population 0.6, 1.3, and 0.9%, respectively. In all three groups, fewer than 30% of patients were known to have this laboratory abnormality before screening. The incidence of cardiovascular disease was high in the macroalbuminuria group (e.g., the age- and gender-adjusted hazard ratio for mortality as a result of cardiovascular disease is 2.6 [1.1 to 6.0]) and for the impaired renal function group (3.4 [1.5 to 8.0]). After a mean follow-up of 4.2 yr, the macroalbuminuria group showed a -7.2 ml/min per 1.73 m2 estimated GFR (eGFR) loss, compared with -2.3 ml/min per 1.73 m2 in the control group (difference P < 0.001), whereas the rate of eGFR loss in the impaired renal function group (-0.2 ml/min per 1.73 m2; P = 0.18) and the erythrocyturia group (-2.6 ml/min per 1.73 m2) was not different from the control group. Macroalbuminuria and impaired renal function both predict a worse prognosis with respect to cardiovascular morbidity and mortality. However, macroalbuminuria is a better risk marker than low eGFR or erythrocyturia to identify in population screening of individuals who are at risk for accelerated GFR loss.