Establishment of a Method to Detect Microalbuminuria by Measuring the Total Urinary Protein-to-Creatinine Ratio in Diabetic Patients

Establishment of a Method to Detect Microalbuminuria by Measuring the Total Urinary Protein-to-Creatinine Ratio in Diabetic Patients

KYOKO YAMAMOTO,^1,2 YASUHIRO KOMATSU,² HIROYUKI YAMAMOTO,² HIROKO IZUMO,³ KYO SANOYAMA,³ MASAMI MONDEN,³ KYOKO TAKEDA,^3,4 FUMIKO NAKAHARA⁴ and KATSUMI YOSHIDA¹

¹Department of Laboratory Medicine and Clinical Science, Tohoku University Graduate School of Medicine, Sendai, Japan
²Division of Nephrology, Department of Internal Medicine, St. Luke's International Hospital, Tokyo, Japan
³Division of Endocrinology and Metabolism, Department of Internal Medicine, St. Luke's International Hospital, Tokyo, Japan
⁴Clinical Laboratory Department, St. Luke's International Hospital, Tokyo, Japan

Diabetes and chronic kidney disease (CKD) which are risk facters of cardiovascular disease, are increasing global public health problems. Microalbuminuria is an early sign of progressive cardiovascular and renal disease in individuals with or without diabetes. Screening for microalbuminuria and early treatment are recommended for patients with increased cardiovascular and renal risk factors. However, the procedure used to measure urinary albumin is expensive. Alternatively, the measurement of total urinary protein is simple and inexpensive. Thus, we aimed to establish a method that could predict the presence of microalbuminuria by measuring the total protein-to-creatinine ratio. Spot urine samples were obtained from 150 patients with diabetes mellitus, and the total protein-to-creatinine ratio and the albumin-to-creatinine ratio (ACR) were measured. There was a significant positive correlation between the protein-to-creatinine ratio and the ACR (r = 0.95). The presence of albuminuria (both micro- and macroalbuminuria) could be predicted from the value of the protein-to-creatinine ratio in more than 90% of patients. A receiver-operating characteristic curve analysis revealed that the protein-to-creatinine ratio had a sensitivity and a specificity of 90.8% and 91.9%, respectively, for the detection of albuminuria and a cutoff value of 0.091 g/g creatinine. These results suggest that screening for microalbuminuria can be replaced by the detection of the protein-to-creatinine ratio, which may be cost-effective for patients with cardiovascular risks as well as for the general population.

keywords —— albumin-to-creatinine ratio; cardiovascular disease; diabetes mellitus; microalbuminuria; protein-to-creatinine ratio

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Tohoku J. Exp. Med., 2011, 225, 195-202

Correspondence: Yasuhiro Komatsu, Division of Nephrology, Department of Internal Medicine, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo 104-8560, Japan.

e-mail: komayasu@luke.or.jp