Urinary Total Protein as the Predictor of Albuminuria in Diabetic Patients

BACKGROUND: In order to detect nephropathy, measurement of total (24 hrs) urinary albumin or albumin/creatinin ratio in random urine samples is being recommended. But methods of albumin measurement are not available in all laboratories and also cost about 6 times more than that of urinary total protein measurement. OBJECTIVES: This Study was performed to determine appropriate cut off point in 24 hours urine total protein to diagnose micro- and macroalbuminuria in patients with diabetes mellitus. PATIENTS AND METHODS: In this study, 204 patients with diabetes mellitus type I and II were selected. In collected 24 hours urine from patients, protein and albumin were measured by using Pyrogallol and Immunoturbidimetry methods, respectively. RESULTS: Normoalbuminuri (albumin < 30 mg/24 hrs urine), microalbuminuri (albumin = 30-300 mg/24 hrs urine), and macroalbuminuri (albumin > 300 mg/24 hrs urine) were detected in 130, 51, and 23 patients, respectively. In 24 hrs urine collections, amounts of protein and albumin were compared to calculate cut off point of exerted protein for nephropathy diagnosis. cut off point of 73 mg/day for urinary total protein had appropriate sensitivity (94.5 %, CI = 91.4 % -97.6 %) and specificity (77.9 %, CI = 72.8 % -82.9 %) for microalbuminuria, while cut off point of 514 mg/day (sensitivity 95.7 %; specificity 98.9 %) was detected for diagnosis macroalbuminuria. Urine protein exertion of 150 mg/day that is currently considered as a normal value in most laboratory kits had a sensitivity of 73.1 % by which 30 % of microalbuminuric cases remained undiagnosed. CONCLUSIONS: Urinary total protein cut-off points of 73 mg/day and 514 mg/day were diagnostic for micro- and macroalbuminuria, respectively.