To What Extent Modified Methylene Blue Test Can Help in Urinary Tract Infections' Screening?
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- Category: Vol. 85, September 2017
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To What Extent Modified Methylene Blue Test Can Help in Urinary Tract Infections' Screening?, AMIRA M. MOKHTAR, MARWA A. EL-ASHRY, MAHA A. BEHAIRY and AYA S. ROSHDY
Abstract
Background: Urinary tract infection is one of the most common serious health problems that affect millions of people each year. A precise diagnosis prevents unnecessary use of antibiotics. Urine culture is the gold standard method for diagnosis although expensive and time consuming. Usage of an effective rapid screening method for urine samples could reduce the number of urine samples cultured that ultimately would not grow significant levels of uropathogens. This study aimed at evaluation the use of modified methylene blue test as a rapid screening method for significant bacteriuria.
Methods: One thousand urine samples were collected from patients clinically suspecting urinary tract infection (patient group) and another one hundred samples were collected from apparently healthy individuals (control group). All collected samples were subjected to urine analysis, semi quantitative urine culture, and modified methylene blue test.
Results: Regarding urine culture, among the clinically suspected group 18.9% were positive cultures, 76.7% of them had significant bacterial growth of ³105 CFU/ml and 23.2% had non-significant growth (104-105), while 81.1% were negative cultures. Among the samples screened by modified methylene blue test, 23.2% had absorbance above the cut-off value (0.64) and so were recorded as being positive for significant bacteriuria. The presence of albumin, blood, casts, crystals, amorphous, bilirubin, pus or red blood cells in urine had significant statistical association with both modified methylene blue test and culture results. Modified methylene blue test was found to have 89.3% specificity, 76.7% sensitivity, positive predictive value of 62.5% and negative predictive value of 94.3% when compared to conventional urine culture as the standard method.
Conclusion: Modified methylene blue test is a rapid screening test for urinary tract infections with average sensi-tivity and high specificity thatcanimprove the overall turn-around time of negative results and reduce laboratory culture workload.