Association between albuminuria and proteinuria in the general population: the AusDiab Study

Background. The relationship between urinary albumin and total protein excretion and the appropriateness of one test over the other are unclear due to the paucity of large epidemiological studies of albuminuria and proteinuria. In screening for renal and cardiovascular disease, whether to measure albuminuria, proteinuria or both, is currently an unanswered question. Methods. Random urine samples from 10 596 (94.2%) participants of the Australian Diabetes, Obesity and Lifestyle Study were tested for albuminuria (urine albumin:creatinine greater than or equal to30mg/g) and proteinuria (urine protein:creatinine greater than or equal to0.20mg/mg). This study was a representative sample of the national non-institutionalized population drawn from 42 randomly selected urban and non-urban areas (census collector districts) across Australia. Results. Among a representative cross-section of the Australian adult population, urine albumin excretion was strongly correlated with total protein excretion, particularly among the elderly, and those with diabetes mellitus, hypertension, obesity and renal impairment (P < 0.001). Albuminuria performed well as a screening test for proteinuria: sensitivity 91.7% [95% confidence interval (CI) 87.7-94.5%], specificity 95.3% (95% CI 94.9-95.7%) and negative predictive value 99.8% (95% CI 99.7-99.9%). However, among those with proteinuria, 8% excreted albumin within the normal range. Conclusions. While albuminuria may be a suitable test for general population screening for renal and cardiovascular disease, it should not replace testing for proteinuria in those with known or suspected renal disease.