Diabetic patients with microalbuminuria are at a high risk for developing overt nephropathy and cardiovascular complications (1). Constant monitoring is mandatory to prevent vascular complications. Due to socioeconomic reasons, many patients in developing countries cannot afford to regularly test their blood glucose. In such a scenario, the test of urine albumin-to-creatinine ratio or albumin excretion rate to diagnose diabetic albuminuria is beyond the reach of many patients. In addition, only a few speciality centers provide facilities for doing these tests. Urine protein dipstick testing is, however, easily available to most patients. We aimed to evaluate whether a dipstick test showing “trace” for urinary protein reliably indicated the presence of microalbuminuria.
Urine dipstick for protein was done in 500 consecutive random urine samples of type 2 diabetic subjects, using Uristik (Bayer Diagnostics India). The results were read visually as “negative” or as “positive,” indicated as trace, 1+, 2+, or greater, representing a protein concentration of <0.15, 0.15–0.30, >0.30, or >1 g/l, respectively. Three trained technicians tested all samples, and the interobserver variations were <5%, measured statistically. Urine microscopy was done on all samples, and samples with significant presence of white blood cells and other cell types were excluded.
Among the 500 urine samples, 360 were negative for dipstick, 99 were trace, and 41 were 1+ or greater. In the subjects without clinical proteinuria (n = 459), albumin-to-creatinine ratio was determined. The results were ranked as normoalbuminuria (men <2.5, women <3.5 mg/mmol [n = 356]) and microalbuminuria (men 2.5−25, women 3.5–35 mg/mmol; n = 103). Quantification of urine creatinine (mg/dl) was by the Jaffe method, urine albumin by immunoturbidimetry, and urine protein by the biuret method using a Hitachi 912 analyzer (Roche, Mannheim, Germany).
The data of 459 urine samples were used to determine the sensitivity and specificity of the dipstick to detect a negative or a positive test. The sensitivity, specificity, positive predictive value, and negative predictive value of trace to detect microalbuminuria were 68, 98, 92, and 88%, respectively; the accuracy was 89%.
This study showed that the dipstick test with a reading of trace was highly specific and fairly sensitive in determining the presence of microalbuminuria.
Micral-test II was found to be an effective screening tool in various Caucasian studies (2). However, even micral-test II is an expensive screening tool in developing countries. In a study by Baskar et al. (3), Combur 5 test D strips (Roche Diagnostics, Vilvoorde, Belgium) were found to have little or no benefit in repeat testing outside the low microalbuminuric range. In our study, we found that the positive test had 98% sensitivity and 100% specificity to determine proteinuria.
In developing countries like India, the cost of doing an albumin-to-creatinine ratio in a random sample is $5.60 U.S. (INR 250), while 100 patients can be screened for albuminuria by a dipstick at the cost of $9.80 U.S. (INR 439). A repeat test is, however, essential in positive cases to ascertain the presence of microalbuminuria or proteinuria. The cost efficiency and the high sensitivity and specificity of the urine dipstick test will encourage its use among primary care physicians and private practitioners as a diagnostic tool for microalbuminuria and proteinuria. This would initiate the first step toward detection of incipient diabetic nephropathy in developing countries.
