A study of patients with chronic kidney disease (CKD) found a substantial excess risk for CKD progression and kidney failure as albuminuria (protein in the urine) increased, even at levels below 30 mg/g. These findings raise questions about the best time to start treatment to reduce protein in urine, and whether lowering albumin levels further could improve health outcomes in people with CKD who already have relatively low levels of albumin in their urine. The findings are published in Annals of Internal Medicine.

Albuminuria is a major risk factor for CKD progression, especially when categorized as moderate (30 to 300 mg/g) or severe (>300 mg/g). However, there are limited data on the prognostic value of albuminuria within the normal range.

Researchers from Boston University Chobanian & Avedisian School of Medicine studied 1,629 participants in the CRIC (Chronic Renal Insufficiency Cohort) study to estimate the increase in the cumulative incidence of CKD progression with greater baseline levels of albuminuria among persons with CKD who had normoalbuminuria (<30 mg/g).

Levels of albumin and creatinine in urine samples were used to calculate urine albumin-to-creatinine ratio (UACR), an important marker of kidney health. The authors then looked at how this marker, along with other factors, was related to the progression of CKD over 10 years, considering potential factors that could influence the results.

The data showed that participants who had higher levels of albumin in their urine were more likely to experience worsening kidney disease or kidney failure. Specifically, the 10-year absolute risk differences among persons with a UACR of 15 mg/g or more compared with persons with UACRs of 5 to less than 15 mg/g and 0 to less than 5 mg/g were 7.9% and 10.7% higher for CKD progression and 5.1% and 6.3% for kidney failure, respectively.

These results remained robust when comparing persons with UACRs of 10 mg/g or more versus those with UACRs of less than 10 mg/g. The findings were independent of several covariates, including baseline kidney function.