Urinary Haptoglobin Predicts Rapid Renal Function Decline in Asians With Type 2 Diabetes and Early Kidney Disease.

CONTEXT: A recent study suggested that urinary haptoglobin may be a novel biomarker to improve predictive performance of albuminuria in type 2 diabetes mellitus (T2DM). However, the finding has not been externally validated.

OBJECTIVE: The objective of the study was to evaluate whether urinary haptoglobin improves predictive performance of albuminuria in Asian T2DM with an estimated glomerular filtration rate (eGFR) of 30 mL/min per 1.73 m2 or greater.

DESIGN AND PARTICIPANTS: This was a prospective study with 269 T2DM nonprogressors (eGFR changes 0.2 [-0.7 to 1.0] mL/min per 1.73 m2 per y) and 153 T2DM progressors (eGFR decline -7.1 [-10.6 to -5.1] mL/min per 1.73 m2 per y) included.

MAIN OUTCOME: The main outcome was an eGFR decline of 3 mL/min per 1.73 m2 or greater per year by trajectory slope.

RESULTS: Urinary haptoglobin level increased 11-fold in progressors as compared with nonprogressors at baseline. In comparison with subjects in the lowest quartile, those with haptoglobin in the third and fourth quartiles had 2.25- (1.11-4.59) and 5.41 (2.63-11.1)-fold increased odds for renal progression, whereas those with an albuminuria level in the third and fourth quartiles had 2.53- (1.17-5.51) and 9.01 (4.00-20.5)-fold increased odds. Notably, urinary haptoglobin predicted renal progression independent of albuminuria. Addition of haptoglobin significantly improved the predictive performance of albuminuria beyond traditional risk factors as reflected by a significant increase in the net reclassification index and integrated discrimination index. In the chronic kidney disease stage 3 subpopulation, urinary haptoglobin outperformed albuminuria for the prediction of rapid renal function decline.

CONCLUSIONS: Our data confirmed that urinary haptoglobin may improve the predictive performance of albuminuria for renal progression in Asians with T2DM. Moreover, it may potentially outperform albuminuria for the prediction of rapid renal function decline in the T2DM chronic kidney disease stage 3 subpopulation.