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Uriglox and quantitative urine microscopy in diagnosis of urinary tract infection
Abstract:
The aim of this study was to find an alternative to the sole use of abundant cultural findings as a basis for the diagnosis of urinary tract infection (UTI). For this purpose, the results obtained from the bacteriological culture of daytime urine specimens from 154 students by the dip slide method were checked against the findings from the quantitative culture, microscopy and Uriglox testing of the first morning urines voided later at home. As a diagnostic criterion, the finding of 10(5) or more bacteria/ml urine in two successive cultures had an error of 19%. For the simultaneous occurrence in the morning urine of abundant bacteria (larger than or equal to 10(5)/ml) and a subnormal glucose concentration (as revealed by the Uriglox test), this error was 1.5%. Only the latter combination showed, therefore, the presence of UTI at the confidence level of larger than or equal to 95%, or was "clinically significant". The specificity indices for the Uriglox test and the quantitative culture were 0.99 and 0.97, respectively. Microscopy of the morning urine showed 10(3) or more bacteria/ml in all the subjects with infection but the number of leucocytes was normal in a fifth of them. The specificity indices for microscopic counts of 10(3) or more organisms/ml and 10 or more leucocytes/mm3 were 0.74 and 0.94, respectively. For higher counts, i.e. 10(5) or more bacteria/ml and 50 or more leucocytes/mm3, the specificity index of positive microscopy was 1.0. This specificity level was, however, attained at the expense of the sensitivity, which for 10(5) or more organisms/ml was 0.67 and for 50 or more leucocytes/mm3 0.53. It is concluded that abundant bacterial contamination of specimens often decisively complicates the diagnostic use of urine culture, and therefore the combined use of quantitative culture, microscopy and the Uriglox test is recommended as the principal tool for the diagnosis of UTI in ordinary hospital and ambulatory health services.