The Efficacy of Urinary Albumin-to-Osmolality Ratio in Predicting 24-hour Urine Albumin Excretion in Type 2 DM Patients

Lee, Ju Hyun; Kim, So Young; Lee, Min Ji; Kim, Soon Ae; Shin, Sung Joon; Kim, Kyung Soo

Abstract

PURPOSE
Microalbuminuria is a predictive marker for early diabetic nephropathy and an independent risk factor for cardiovascular disease. Screening for the presence of microalbuminuria is one of the best ways to detect early kidney damage in patients with diabetes or other disease, and also is of great significance in prevention of cardiovascular disease. Recently spot urine albumin-to-creatinine ratio (ACR) has been proposed as a screening test for microalbuminuria. However, the creatinine level is affected by diet, drugs, age, muscle mass and race, etc. The cutoff value for ACR has generated some controversy. In this report, we evaluated the efficacy of spot urine albumin-to-osmolality ratio (AOR) in order to predict 24-hour urine albumin excretion (AER).
METHODS
Seventy-three patients diagnosed as type 2 DM in DUIH were recruited. Urine was collected for 24 hours for the measurement of microalbumin and first morning urine was obatined for the measurement of ACR and AOR. We evaluated the correlation of AER and ACR or AOR.
RESULTS
Correlation between spot urine AOR and 24 hour urine AER (Spearmans' rho=0.804, p<0.01) was similar to that between ACR and AER (Spearman's rho=0.872, p<0.01). Also correlation analysis revealed that AOR is closely correlated with ACR (Spearman's rho=0.939, p<0.01). We evaluate accuracy of spot urine ACR and AOR using receiver operating characteristics (ROC) curve, AUC were 0.97, 0.94, respectively.
CONCLUSION
AOR correlates closely with AER. Both AOR and ACR are effective predictors of microalbuminuria. Therefore AOR is an alternative to ACR in the detection and follow-up of microalbuminuria in patients with DM.