Resumen de Performance of a veterinary urine dipstick paddle system for diagnosis and identification of urinary tract infections in dogs and cats
Objective�To evaluate the performance of a veterinary urine dipstick paddle (UDP) for diagnosis and identification of urinary tract infection (UTI) in dogs and cats.
Design�Prospective, randomized, blinded study.
Sample�207 urine specimens.
Procedures�UDPs were inoculated by 2 investigators and incubated according to manufacturer's instructions. Results, including presence or absence of bacterial growth, organism counts, and identification of uropathogens, were compared between investigators and with microbiology laboratory results. A subset of UDPs with bacterial growth was submitted to the laboratory for confirmation.
Results�The laboratory reported 64 (30.9%) specimens had growth of bacteria. Bacterial growth was reported for 63 (30.4%) and 58 (28.0%) of the UDPs by investigators 1 and 2, respectively. Sensitivity and specificity of the UDP for detection of bacterial growth were 97.3% and 98.6%, respectively, for investigator 1 and 89.1% and 99.3%, respectively, for investigator 2. For UPDs with = 105 colony-forming units/mL, organism counts correlated well between the laboratory and investigators 1 (r = 0.95) and 2 (r = 0.89). Pathogen identification was not always accurate. Only 25 of 33 (75.8%) UDPs submitted for confirmation yielded bacteria consistent with those isolated from the original bacterial culture of urine.
Conclusions and Clinical Relevance�The veterinary UDP system was a sensitive test for screening patients for bacterial UTI, but uropathogen identification was not always accurate. When UDPs have bacterial growth, a fresh urine specimen should be submitted to the laboratory to confirm the identity of the organisms and to permit antimicrobial susceptibility testing.
Approximately 14% of dogs develop a bacterial UTI during their lifetime, with a variable age of onset.1 Bacterial cystitis is less common in young cats than in old cats, but infections are more common in older cats, most likely because of the presence of other comorbidities such as hyperthyroidism and diabetes mellitus.2,3 Although UTIs can comprise mixed bacterial infections, most UTIs involve a single bacterial species. Escherichia coli is the pathogen most commonly isolated from the urine of cats and dogs, followed by Staphylococcus spp, Proteus spp, Klebsiella spp, Enterococcus spp, and Streptococcus spp.4 The collection of urine by use of cystocentesis followed by complete urinalysis and QABC is recommended to confirm a bacterial UTI for dogs or cats with signs of lower urinary tract disease.5 If it is not possible to obtain a sample with cystocentesis, collection of a urine sample by use of a urinary catheter is considered acceptable, provided QABC is performed. Quantitative aerobic bacterial culture of urine provides an estimate of the number of bacteria present and is important when determining whether the bacteria are clinically relevant. The number of organisms that constitutes clinically relevant bacteriuria for the various collection methods in dogs and cats has been reported.6 Because of the expense, veterinarians do not always submit urine for QABC and antimicrobial susceptibility testing. Instead, empirical antimicrobial treatment is often started for a presumptive diagnosis of UTI made on the basis of clinical signs of lower urinary tract disease with or without results for bacterial culture of urine. Repeated treatment of animals with recurrent lower urinary tract signs without consideration of QABC and antimicrobial susceptibility test results may lead to incorrect antimicrobial choices, unnecessary adverse effects of drug treatment, and possible selection of resistant bacterial populations. Widespread antimicrobial resistance is an emerging problem in small animal medicine7 and in humans.8 Urine dipstick paddles (also known as dip slides or paddle testers) have been used for decades in human medicine for the detection of bacterial cystitis.9�12 In humans, the overall reported sensitivity of UDPs is 73% to 99% with a specificity of 94% to 99%, compared with results of QABC performed in a diagnostic microbiology laboratory as the criterion-referenced standard.13,14 The bacterial species is correctly identified in 54% to 95% of samples,15 but the proportion of bacteria correctly identified is lower when multiple organisms are present.16,17 Recently, a UDP system has been marketed for in-clinic veterinary use. The system consists of a culture paddle embedded with 2 standard culture media (one side with cysteine lactose electrolyte�deficient medium, and the other side with eosin methylene blue medium), which support the growth of the uropathogens that most commonly cause UTIs in dogs and cats. Culture results for these UDPs are reported by the manufacturer to be highly correlated (99%) with results for a reference laboratory culture method. If substantial bacterial growth is detected, the manufacturer recommends submission of the UPD to a reference laboratory for confirmation of the organisms and antimicrobial susceptibility testing because antimicrobial susceptibility information cannot be obtained from the UPDs. Such UDPs have the potential to be an inexpensive means for veterinarians to screen for UTIs before initiation of antimicrobial treatment. They could be particularly useful when culture results of the UPDs are negative, which therefore could decrease the use of inappropriate empirical antimicrobial treatment.
The objective of the study reported here was to compare results of bacterial culture and quantitation of bacterial numbers as determined with the veterinary UDP system with those determined with QABC performed at a microbiology laboratory. We also compared various methods of inoculation of the UDP and examined level of agreement between users of the UDP.
