Association between GFR, proteinuria, and adverse outcomes among White, Chinese, and South Asian individuals in Canada

Background: We investigated the association between proteinuria, estimated glomerular filtration rate (eGFR), and risk of mortality and kidney failure in white, Chinese, and South Asian populations.

Study design: Population-based cohort study.

Setting & participants: Participants from Alberta, Canada, with a serum creatinine and urine protein dipstick measurement from January 1, 2005, to December 31, 2005.

Predictor: White, Chinese, or South Asian ethnicity.

Outcomes: Prevalence of proteinuria by level of eGFR (estimated using the MDRD [Modification of Diet in Renal Disease] Study equation) and the association between eGFR, proteinuria, and all-cause mortality and kidney failure.

Measurements: Rates of all-cause mortality and kidney failure per 1,000 person-years were calculated using Poisson regression by ethnicity, eGFR level, and proteinuria level while adjusting for sociodemographic variables and comorbid conditions.

Results: Of 491,729 participants, 5.3% were Chinese and 4.7% were South Asian. For participants with eGFR <60 mL/min/1.73 m(2), the prevalence of heavy proteinuria was higher in Chinese and South Asians compared with whites. Compared with whites, adjusted rates of death were significantly lower for Chinese and South Asian populations (rate ratios, 0.67 [95% CI, 0.56-0.80] and 0.73 [95% CI, 0.59-0.88], respectively); these rate ratios did not vary by eGFR and proteinuria levels.

Limitations: Using surname to identify ethnicity has the potential for misclassification due to name changes and identical last names from different ethnic groups. Also, to be eligible for inclusion, participants had to have a measurement of serum creatinine and urine dipstick proteinuria.

Conclusions: Although increasing proteinuria and lower eGFR predicted mortality and progression to kidney failure in all 3 ethnic groups, both Chinese and South Asian populations experienced a lower risk of death and similar risk of kidney failure compared with whites at all eGFR and proteinuria levels. Studies exploring this association further are required.