Evaluation of Screening Methods for the Detection of Urinary Tract Infection

Abstract

Background: Urinary tract infection occurs in all populations, but with particular impact in females of all ages, male at the two extremes of their life, renal transplant patients, and anyone with functional or structural abnormalities of the urinary system.

Method: Evaluation of reagent strips, unspun gram stain urine and wet mount as a screening tests for urinary tract infection was done from March 20 to May 30, 2000. A cross sectional study was done on 300 patients attending Jimma hospital. Ona morning midstream urine collected from these patients, semi-quantitative culture, biochemical tests for nitrite, leucocyte esterase, blood and protein using a commercial reagent strip, waspun gram stain and wet mount were done. The data obtained from this study was analysed using EPI-Info statistical package for sensitivity, specificity and predictive values.

Result: Using the culture result as a gold standard, the unspun gram stain urine demonstrated the highest sensitivity and negative predictive value (95% and 99% respectively). A single chemical test has not been found to be efficient in detecting significant bacteriuria; however, accuracy increased as the number of combination increased. When a positive result from any one of the above mentioned screening tests were used to indicate the presence of infection, a sensitivity of 88%, specificity of 75% a positive predictive value of 7% and an impressive negative predictive value of 96% were achieved. In agreement with the result elsewhere this study doesn't support the diagnosis of urinary tract infection on the basis of pyuria alone. The minimum number of bacteria per oil immerssion field that correlate with a 10 CFU/ml is found to be about 20 nor 21 as stated in previous studies.

Conclusion: There is no single test for bacteriuria which gives an immediate and infallible result from the above screening tests unspunt gram stain urine and combination of chemical tests are simple and reliable screening tests in detecting urinary tract infection. This study recommends the application of these tests as routine test in screening UTI.