Use of rapid screening tests in processing urine specimens by conventional culture and the AutoMicrobic system

Two rapid urine screening tests, the Chemstrip LN (BioDynamics, Indianapolis, Ind.) and the Bac-T-Screen urine screening device (Marion Laboratories, Inc., Kansas City, Mo.), were evaluated as techniques to predict bacteriuria as quantitated by either conventional culture or the AutoMicrobic system (Vitek Systems, Inc., Hazelwood, Mo.). A total of 666 urine specimens were analyzed by both screening tests as well as the AutoMicrobic system and quantitative culture. The sensitivities of both Chemstrip LN and Bac-T-Screen for the detection of low levels of bacteriuria (greater than or equal to 10(3) CFU/ml) were comparable (73.3 and 74.4%, respectively) and were too low to recommend their use as a primary urine screen. Their excellent predictive value of a negative result at the 10(5) CFU/ml level (96 and 97.5%, respectively) makes them potentially useful in predicting urine specimens with less than 10(5) CFU/ml. The use of either of these tests in combination with the AutoMicrobic system markedly decreased the time required to classify urine specimens. Their low cost relative to the AutoMicrobic system urine card makes the use of either test cost effective as a screen for the AutoMicrobic system.