Association of Spot Urine Albumin-to-Creatinine Ratio and 24 Hour-Collected Urine Albumin Excretion Rate in Patients with Type 2 Diabetes Mellitus

Abstract

Background: Measuring urine albumin in diabetic patients is an important screening test to identify those individuals at high risk for cardiovascular disease and the progression of kidney disease. Recently, spot urine albumin-to-creatinine ratio (ACR) has replaced 24 hour-collected urine albumin excretion rate (AER) as a screening test for microalbuminuria given its comparative simplicity. The purpose of the current study was to evaluate the degree of correla tion between AER and ACR in the normal, microalbuminuric and macroalbuminuric ranges, and to identify the lower limits of ACR for both genders. Methods: A total of 310 type 2 diabetics admitted to one center were enrolled in the present study. Following the collection of a spot urine sample, urine was coll ected for 24 hours and albumin content was measured in both specimens. Results: Mean patient age was 60.2 years. A total of 25.4% had microalbuminuria and 15.8% had macroalbuminuria. The data revealed a strongly positive correlation between AER and ACR across all ranges of albuminuria (R = 0.8). The cut-off value of ACR for 30 mg/day of AER by the regression equation was 24 μ g/mg for men, 42 μ g/mg for women and 31.2 μ g/mg for all patients. The diagnostic performance expressed as the area under the curve (AUC) was 0.938 (95% CI, 0.911-0.965) for ACR. ACR revealed a sensitivity of 84% and specificity of 84%, when a cut-off value of 31.2 μ g/mg was employed. Conclusion: ACR was highly correlated with AER, particularly in the range of microalbuminuria. The gender combined cut-off value of ACR in type 2 diabetic patients was determined to be 31.2 μg/mg However, additional studies of large outpatient populations, as opposed to the inpatient population used in the present study, are required to confirm the utility of this value. (Korean Diabetes J 33:299-305, 2009)