Confirmation of adverse outcomes with proteinuria

In a recently published study (Hemmelgarn et al, JAMA 2010), the adverse outcomes of proteinuria were confirmed by studying almost a million patients. In this mammoth study of 920928 adults in Canada, it was demonstrated that prognosis associated with a given level of eGFR varies substantially based on the presence and severity of proteinuria. In fact, patients with heavy proteinuria but without overtly abnormal eGFR appeared to have worse clinical outcomes than those with moderately reduced eGFR but without proteinuria. Adjusted mortality rates were more than 2-fold higher among individuals with heavy proteinuria measured by urine dipstick and eGFR of 60 mL/min/1.73 m(2) or greater, as compared with those with eGFR of 45 to 59.9 mL/min/1.73 m(2) and normal protein excretion (rate, 7.2 [95% CI, 6.6-7.8] vs 2.9 [95% CI, 2.7-3.0] per 1000 person-years, respectively; rate ratio, 2.5 [95% CI, 2.3-2.7]). Similar results were observed for the outcomes of hospitalization with acute myocardial infarction, end-stage renal disease, and doubling of serum creatinine level. Authors proposed that future revisions of the classification system for CKD should incorporate information on proteinuria. The main limitation of this study is that it is an observational study.