Antibiotic screening of urine culture as a tool for interal quality audit - Abstract

BACKGROUND: Microbiologic culture of urine is an important component in the diagnosis of urinary tract infections (UTI).

However, confounding factors like the patient's current history of antibiotic usage can affect the interpretation of urine culture results.

AIMS: This study was undertaken to find out the occurrence of unreported antibiotic consumption prior to urine culture and its clinical consequences.

METHOD: In this descriptive study conducted from February to August 2013, we tested consecutive urine specimens for the presence of antibiotics with a modified urine antibacterial substance assay (UABA) and compared the results obtained with the accuracy of antibiotic data entry on the accompanying request forms. In addition, the consequences of culturing urine specimens with incomplete antibiotic history received in the laboratory were investigated.

RESULTS: Out of 2,040 urine specimens, 721 (35.34 per cent) were UABA positive. Comparison of antibiotic screening of urine with antibiotic data entry from request forms showed 1,299 (63.68 per cent) true-negative, 38 (1.86 per cent) true- positive, 20 (0.98 per cent) false-negative, and 683 (33.48 per cent) false-positive results. The sensitivity and specificity of this test were 65.52 per cent and 65.54 per cent, respectively. The positive and negative predictive values were 5.27 per cent and 98.48 per cent, respectively. The UABA had a positive diagnostic likelihood ratio of 1.901.

CONCLUSION: This internal audit demonstrates how the accurate history of current antibiotic usage in the request forms impacts the interpretation of urine culture results.

Written by:
Srirangaraj S, Kali A, Charles MP.   Are you the author?
Department of Microbiology, Mahatma Gandhi Medical College & Research Institute, Pondicherry.

Reference: Australas Med J. 2014 Feb 28;7(2):73-7.
doi: 10.4066/AMJ.2014.1956

PubMed Abstract
PMID: 24611076 Infections Section