Detecting microalbuminuria by urinary albumin/creatinine concentration ratio

Background. Microalbuminuria, i.e. a subclinical increase of the albumin excretion rate in urine, may be a novel atherosclerotic risk factor. This study aimed to test whether microalbuminuria can be identified by measurement of urinary albumin concentration or urinary albumin/creatinine concentration ratio, instead of the usual measurement of the albumin excretion rate in a timed urine collection. Methods. All 2579 subjects analysed were screened in a population based epidemiological study. Participants with diabetes mellitus, renal disease, haematuria, or urinary tract infection were not included. Urinary albumin (U(alb)) and creatinine (U(creat) concentrations were measured in an overnight collected sample by enzyme-linked immunosorbent and colorimetric assays, respectively. Urinary albumin excretion rate (UAER) and urinary albumin/creatinine concentration ratio (U(alb)/U(creat)) were calculated. Results. The correlation between U(alb) and UAER was 0.72 (n = 2579, P < 0.001), and the correlation between U(alb)/U(creat,) and UAER was 0.81 (n = 2579, P < 0.001). In the detection of microalbuminuria, the nosographic sensitivity and specificity, and the diagnostic specificity were 58%, 97%, and 66% for U(alb), and 73%, 97%, and 73% for U(alb)/U(creat) respectively. Conclusions. It is concluded that measurement of the albumin/creatinine concentration ratio is a specific and quite sensitive alternative to measurement of the urinary albumin excretion rate in timed collections, when screening for microalbuminuria.