Detection of bacteriuria and pyuria by URISCREEN, a rapid enzymatic screening test

Abstract

A multicenter study was performed to evaluate the ability of the URISCREEN (Analytab Products, Plainview, N.Y.), a 2-min catalase tube test, to detect bacteriuria and pyuria. This test was compared with the Chemstrip LN (BioDynamics, Division of Boehringer Mannheim Diagnostics, Indianapolis, Ind.), a 2-min enzyme dipstick test; a semiquantitative plate culture method was used as the reference test for bacteriuria, and the Gram stain or a quantitative chamber count method was used as the reference test for pyuria. Each test was evaluated for its ability to detect probable pathogens at ≥102 CFU/ml and/or ≥1 leukocyte per oil immersion field, as determined by the Gram stain method, or >10 leukocytes per μl, as determined by the quantitative count method. A total of 1,500 urine specimens were included in this evaluation. There were 298 specimens with ≥102 CFU/ml and 451 specimens with pyuria. Of the 298 specimens with probable pathogens isolated at various colony counts, 219 specimens had colony counts of ≥105 CFU/ml, 51 specimens had between 104 and 105 CFU/ml, and 28 specimens had between 102 and <104 CFU/ml. Both the URISCREEN and the Chemstrip LN detected 93% (204 of 219) of the specimens with probable pathogens at ≥105 CFU/ml. For the specimens with probable pathogens at ≥102 CFU/ml, the sensitivities of the URISCREEN and the Chemstrip LN were 86% (256 of 298) and 81% (241 of 298), respectively. Of the 451 specimens with pyuria, the URISCREEN detected 88% (398 of 451) and the Chemstrip LN detected 78% (350 of 451). There were 204 specimens with both ≥102 CFU/ml and pyuria; the sensitivities of both methods were 95% (193 of 204) for these specimens. Overall, there were 545 specimens with probable pathogens at ≥102 CFU/ml and/or pyuria. The URISCREEN detected 85% (461 of 545), and the Chemstrip LN detected 73% (398 of 545). A majority (76%) of the false-negative results obtained with either method were for specimens without leukocytes in the urine. There were 955 specimens with no probable pathogens or leukocytes. Of these, 28% (270 of 955) were found positive by the URISCREEN and 13% (122 of 955) were found positive by the Chemstrip LN. A majority of the false-positive results were probably due, in part, to the detection of enzymes present in both bacterial and somatic cells by each of the test systems. Overall, the URISCREEN is a rapid, manual, easy-to-perform enzymatic test that yields findings similar to those yielded by the Chemstrip LN for specimens with both ≥102 CFU/ml and pyuria or for specimens with ≥105 CFU/ml and with or without pyuria. However, when the data were analyzed for either probable pathogens at <105 CFU/ml or pyuria, the sensitivity of the URISCREEN was higher (P < 0.05).