A COMPARISON OF CHEMICAL DIPSTICKS READ VISUALLY OR BY PHOTOMETRY IN THE ROUTINE SCREENING OF URINE SPECIMENS IN THE CLINICAL MICROBIOLOGY LABORATORY

Two different commercially available urine dipsticks were evaluated to determine their usefulness as a screening test for the detection of n on-infected urine specimens. The reactions of both dipstick strips wer e read visually and, in addition, one was read by semi-automated refle ctance photometry. 2928 consecutive routine urine specimens received b y the microbiology laboratory during normal working hours underwent te sting by the conventional method of microscopy and culture and the res ults were compared with those obtained by dipstick testing. There were poor correlations between microscopy for red and white blood cells an d dipstick results for blood and leucocyte esterase respectively. The dipsticks had a low positive predictive value (PPV) in identifying inf ected urines. In contrast, dipsticks had a very high negative predicti ve Value (NPV) of 98.6-99.5% and correctly identified a significant pr oportion (about 113) of non-infected urines as reported by the convent ional method. Introduction of dipstick testing of urine specimens in o ur hospital has led to significant time saving as dipstick-negative ur ines are not processed further (except for specific clinical indicatio ns) and there has also been a significant decrease (25%) in the number of specimens submitted to the laboratory. Further efficiencies may be obtainable with increased automation.