How effective are screening tests for microalbuminuria in random urine specimens?

The effectiveness of four urine screening tests-microalbumin (MAlb), total protein (TProt), total protein/creatinine ratio (TProt/Cr R), and dipstick (DPalb) test fur albumin-were evaluated For the detection of MAlb in random urine specimens. The following criteria were used to assess the effectiven ess of each urine screening test: 100% specificity (no false positive resul ts); cost effectiveness; rapidity and ease of performing the screening test ; and increased laboratory efficiency. A "gold standard" for presence of MA lb in random urine samples was defined as a microalbumin/creatinine ratio ( MAlb/Cr R) of greater than or equal to 30 mg/g. The least costly urine scre ening test was the DPalb, which, if assigned a value of 1.0, allowed a cost ranking order for the screening tests-DPalb (1.0) < urine TProt (1.03) < u rine TProt/Cr R (2.1) < urine MAlb (7.0). Two hundred urine samples from di abetic inpatients and outpatients were tested. Only two screening tests-MAl b and DPalb-achieved 100% specificity without increasing laboratory costs ( small net savings), whereas the other two screening tests-TProt and TProt/C r R-only achieved 100% specificity with increased laboratory costs. Theoret ical prevalence rate analysis showed that urine MAlb screening would be eff ective at all prevalence rates for overt nephropathy. TProt and DPalb urine screening testing would be most effective in populations with prevalence r ates of greater than or equal to 15% for overt nephropathy. The TProt/Cr R ratio would only be effective in populations with prevalence rates of great er than or equal to 30%. Of the four urine screening tests, only DPalb woul d significantly streamline the process of measuring urine MAlb. The dipstic k test is inexpensive, easy and rapid to perform, does not delay measuring the ratio, since there is no wait for the screening test result, and can be used by referring laboratories to screen urine specimens before they are s ubmitted to a central laboratory, thereby reducing laboratory workload.