Adverse clinical outcomes associated with a given level of estimated glomerular filtration rate (eGFR) vary substantially based on the presence and severity of proteinuria, according to Canadian researchers.

In a study of 920,985 patients, investigators in Alberta found that those with heavy proteinuria but without overtly abnormal eGFR had worse clinical outcomes than subjects with moderately reduced eGFR but without proteinuria.

“These findings suggest that future revisions of the classification system for CKD should incorporate information from proteinuria,” the authors, led by Brenda R. Hemmelgarn, MD, PhD, of Foothills Medical Center in Calgary, concluded in the Journal of the American Medical Association (2010;303:423-429).

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Over a median follow-up of 35 months, 27,959 patients (3%) died. The adjusted mortality rates were more than two times greater among those with heavy proteinuria (as measured by urine dipstick) and an eGFR of 60 mL/min/1.73 m2 or greater when compared with subjects who had an eGFR of 45-59.9 and normal protein excretion (7.2 vs. 2.9 deaths per 1,000 person-years).

The researchers observed similar results when they measured proteinuria using the albumin-creatinine ratio (15.9 vs. 7.0 deaths per 1,000 person-years). In addition, the adjusted rates of hospitalization for myocardial infarction, progression to end-stage renal disease, and doubling of serum creatinine also were higher in those with an eGFR of 60 or greater and heavy proteinuria than in those with an eGFR of 45-59.9 and normal protein excretion.