Peter Daley1, Yuvraj Gill2, William Midodzi3. 1. Memorial University, St. John's, Canada. Electronic address: pkd336@mun.ca. 2. Royal College of Surgeons, Ireland. 3. Memorial University, St. John's, Canada.
Abstract
INTRODUCTION: Urine specimens for quantitative culture for the diagnosis of urinary tract infection may be unreliable due to bacterial overgrowth within 4 h after collection, at room temperature. Because specimen transportation may take longer than 4 h, urine preservatives may reduce overgrowth. Further evidence is needed to support a recommendation for use of preservative and to compare preservative products. METHODS: Consecutive midstream urine specimens submitted for culture were quantitatively cultured on receipt and then inoculated into 3 storage conditions [BD Urine Vacutainer (BD), Copan UriSwab (US), and refrigeration, with a room temperature control] for 72 h, with quantitative culture performed every 24 h. Odds ratio for significant growth interpretation was reported. RESULTS: Ninety-five of 501 (19.0%) urine specimens demonstrated significant growth. Within 24 h of storage, unpreserved urine at room temperature demonstrated a significantly increased odds ratio for significant growth as compared to preserved urine, and urine in refrigeration demonstrated similar odds ratio for significant growth as compared to preserved. There was no significant difference between the performance of US and BD. Over 48 and 72 h of storage, odds ratio for significant growth further increased. CONCLUSIONS: Preservation performed similarly to refrigeration. Preserved urine demonstrated a doubling in odds ratio for significant growth after 24 h. This increase may negatively impact antibiotic treatment decisions.
INTRODUCTION: Urine specimens for quantitative culture for the diagnosis of urinary tract infection may be unreliable due to bacterial overgrowth within 4 h after collection, at room temperature. Because specimen transportation may take longer than 4 h, urine preservatives may reduce overgrowth. Further evidence is needed to support a recommendation for use of preservative and to compare preservative products. METHODS: Consecutive midstream urine specimens submitted for culture were quantitatively cultured on receipt and then inoculated into 3 storage conditions [BD Urine Vacutainer (BD), Copan UriSwab (US), and refrigeration, with a room temperature control] for 72 h, with quantitative culture performed every 24 h. Odds ratio for significant growth interpretation was reported. RESULTS: Ninety-five of 501 (19.0%) urine specimens demonstrated significant growth. Within 24 h of storage, unpreserved urine at room temperature demonstrated a significantly increased odds ratio for significant growth as compared to preserved urine, and urine in refrigeration demonstrated similar odds ratio for significant growth as compared to preserved. There was no significant difference between the performance of US and BD. Over 48 and 72 h of storage, odds ratio for significant growth further increased. CONCLUSIONS: Preservation performed similarly to refrigeration. Preserved urine demonstrated a doubling in odds ratio for significant growth after 24 h. This increase may negatively impact antibiotic treatment decisions.