[Evaluation of chemical urine dipstick for detection of albuminuria]

ABSTRACT

Microalbuminuria is a marker for nephropathy in diabetic patients and recognition of albuminuria is an important step for early detection and evaluation of diabetes complications. To assess the reliability of urine dipstick tests for detection of albuminuria. The first morning urine samples from candidates for urinanalysis were collected and the results of dipstick tests for protein on 200 selected samples recorded. Urine albumin concentration was determined by electroimmunoassay and the level of urine creatinine determined by Jaffe method. The albumin/creatinine ratio was further calculated as an index of urine albumin excretion rate. Comparing with reference method, the sensitivity, specificity, positive predictive value [PV+], and negative predictive value [PV-] of dipstick test for detection of microalbuminuria were calculated. Based on results obtained by dipstick test, 69 urine samples were negative for presence of protein, 51 trace [ +/- ], 22 [1+], 27 [2+], and 31 [3+]. Detection limit of dipstick for urine albumin concentration ranged from 58 to 585 mg/L with a mean of 280 mg/L. When the reference method for detection of protein in urine samples was used, 35 urine specimens were negative for albuminuria, 85 with microalbuminuria, and 80 with macroalbuminuria. Dipstick test was found to produce false positive and negative results of 3 and 25%, respectively. The sensitivity, specificity, PV+, PV- of dipstick test for detection of microalbuminuria were calculated at 70, 86, 96, and 37.5%, respectively. Chemical dipstick test is of poor sensitivity for detection of microalbuminuria. However, the severity of albuminuria among considerable numbers of diabetic patients is high enough to be detectable by urine dipsticks. While the positive predictive value of chemical urine dipstick tests are more or less at acceptable limit, the negative predictive values are controversial and need to be reevaluated by more sensitive and specific methods: