*Contributed equally to this study.
Diagnostic utility and cost-effectiveness of reflex bacterial culture for the detection of urinary tract infection in dogs with low urine specific gravity
Article first published online: 11 MAY 2009
©2009 American Society for Veterinary Clinical Pathology
Veterinary Clinical Pathology
Volume 38, Issue 3, pages 337–342, September 2009
How to Cite
Tivapasi, M. T., Hodges, J., Byrne, B. A. and Christopher, M. M. (2009), Diagnostic utility and cost-effectiveness of reflex bacterial culture for the detection of urinary tract infection in dogs with low urine specific gravity. Veterinary Clinical Pathology, 38: 337–342. doi: 10.1111/j.1939-165X.2009.00147.x
Dr. Christopher, an editor of the journal, was not involved in the peer-review process or decision to publish this article.
- Issue published online: 1 SEP 2009
- Article first published online: 11 MAY 2009
- urinary tract infection;
- urine specific gravity
Background: Urinary tract infections (UTIs) may be subclinical or difficult to detect in dilute urine as sediment abnormalities may not be observed. In our laboratory, bacterial culture is automatically performed (reflex culture) on samples with urine specific gravity (USG)≤1.013 to increase the likelihood of detecting infection. The value of routine culture of dilute urine, however, has not been fully assessed.
Objective: The purpose of this retrospective study was to evaluate the frequency of positive bacterial cultures and analyze the diagnostic utility and cost-effectiveness of culture compared with routine sediment examination for detecting UTI in dilute urine specimens from dogs.
Methods: Urinalysis and concurrent aerobic bacterial culture results were obtained from the electronic medical record system at the University of California–Davis Veterinary Medical Teaching Hospital for samples with USG≤1.013 analyzed from July 1998 through January 2005. Urine collection method, presence of leukocytes and bacteria, bacterial culture results, and clinical diagnosis were recorded. Cost-effectiveness of reflex culture, based on low USG as the sole criterion, was evaluated.
Results: Of 1264 urine specimens, 106 (8.4%) had positive bacterial cultures. Using culture as the gold standard, sediment evaluation had a diagnostic sensitivity of 58.5% and specificity of 98.3% (diagnostic accuracy 94.9%). An additional cost of $60 per patient was incurred, leading to average annual costs of $11,668 for reflex bacterial cultures of all samples with low USG, regardless of collection method. Within our study population, 10 urine samples needed to be cultured for each true positive result.
Conclusions: The sensitivity of urine sediment evaluation is low for UTI in dilute urine samples; however, reflex bacterial culture does not appear to be cost-effective in dogs with USG≤1.013 in the absence of active urine sediment or high clinical suspicion for UTI.