Detection of Bacteriuria by Canine Olfaction

Background. Urinary tract infections (UTIs) are a significant medical problem , particularly for patients with neurological conditions and the elderly. Detection is often difficult in these patients, resulting in delayed diagnoses and more serious infections such as pyelonephritis and life-threatening sepsis. Many patients have a higher risk of UTIs because of impaired bladder function, catheterization, and lack of symptoms. Urinary tract infections are the most common nosocomial infection; however, better strategies are needed to improve early detection of the disease. Methods. In this double-blinded, case-control, validation study, we obtained fresh urine samples daily in a consecutive case series over a period of 16 weeks. Dogs were trained to distinguish urine samples that were culture-positive for bacteriuria from those of culture-negative controls, using reward-based clicker and treat methods. Results. Samples were obtained from 687 individuals (from 3 months to 92 years of age; 86% female and 14% male; 34% culture-positive and 66% culture-negative controls). Dogs detected urine samples positive for 100 000 colony-forming units/mL Escherichia coli (N = 250 trials; sensitivity 99.6%, specificity 91.5%). Dilution of E coli urine with distilled water did not affect accuracy at 1% (sensitivity 100%, specificity 91.1%) or 0.1% (sensitivity 100%, specificity 93.6%) concentration. Diagnostic accuracy was similar to Enterococcus (n = 50; sensitivity 100%, specificity 93.9%), Klebsiella (n = 50; sensitivity 100%, specificity 95.1%), and Staphylococcus aureus (n = 50; sensitivity 100%, specificity 96.3%). All dogs performed with similarly high accuracy: overall sensitivity was at or near 100%, and specificity was above 90%. Conclusions. Canine scent detection is an accurate and feasible method for detection of bacteriuria.