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Round-up of the recent literature on laboratory procedures and diagnostics

01 July 2014, at 1:00am

A urine dipstick test for the detection of urinary tract infections in cats and dogs 

Winnie Ybarra and others, University of California, Davis 

Bacterial urinary tract infections are common in older cats and will also occur in around 14% of dogs during their lifetime. Urine collection and quantitative aerobic bacterial culture provide a definitive diagnostic test. However, on economic grounds, practitioners will often base their presumptive diagnosis on clinical findings and begin empirical antimicrobial treatment. 

The authors evaluated the performance of a urine dipstick paddle test for the diagnosis and identification of UTIs in both species. Such tests have been used for many years to detect human cystitis and a product has been developed with paddles embedded with two standard culture media which support the growth of the main pathogens causing disease in dogs and cats. 

Two investigators conducted tests on 207 urine specimens and their results were compared with standard laboratory cultures. The sensitivity and specificity of the paddle test were 97.3% and 98.6%, respectively for the first investigator and 89.1% and 99.3% for the second. The paddle test was therefore a sensitive screening test for bacterial UTIs but its ability to correctly identify the pathogen was inferior to that of standard culture methods.

Journal of the American Veterinary Medical Association 244 (7): 814-819.

Comparison of serum amyloid A and C-reactive protein as systemic in ammation markers

Michelle Christensen and others, University of Copenhagen, Denmark 

C-reactive protein and serum amyloid A are two major acute phase proteins that show marked increases in concentration in patients with systemic inflammation. The authors compared the diagnostic performance of automated assays for both proteins in the detection of the condition in a retrospective study using samples from 500 dogs. 

There were significant correlations and excellent diagnostic agreement between the two biomarkers. But the serum amyloid A assay detected a wider range of concentrations and had a significantly superior overall diagnostic performance. 

Canadian Veterinary Journal 55 (2): 161- 168.

Correlation of lab assay results with ultrasound findings in cats with pancreatitis

Samuel Oppliger and others, University of Zurich, Switzerland 

Pancreatitis appears to be a common condition in cats but ante-mortem diagnosis is difficult because of the vague clinical signs and non-specific biochemical findings. The authors assessed the level of agreement between a feline pancreas-specific lipase assay and a colorimetric lipase assay with ultrasonography findings in 161 cats with suspected pancreatitis. 

There was substantial agreement between the results of the two lipase tests but only a fair degree of agreement with the ultrasonography findings. The study could not determine whether the lipase assays or the imaging modality provided the more accurate test results and so the findings of each should be interpreted with caution.

Journal of the American Veterinary Medical Association 244 (9): 1,060-1,065.

Stability of bovine viral diarrhoea virus 1 nucleic acid stored under different conditions

Julia Ridpath and others, National Animal Disease Center, Ames, Iowa 

The accuracy of methods used to identify bovine viral diarrhoea virus in bovine foetuses may be affected by the breakdown of foetal tissues during collection and storage. The authors investigated the stability of viral nucleic acid in aborted foetal tissue exposed to different environmental conditions, as measured by polymerase chain reaction. 

Under the conditions tested, brain samples showed higher stability than the alternative sample sites, skin, muscle, ear and two different pooled organ samples. The impact of faecal contamination increased following storage, suggesting that effort should be made to reduce environmental contamination before archiving. 

Journal of Veterinary Diagnostic Investigation 26 (1): 6-9.

Total serum bilirubin as a prognostic factor in idiopathic canine chronic hepatitis

Aida Gomez Selgas and others, Animal Health Trust, Newmarket 

In human medicine, total serum bilirubin is commonly used as a prognostic factor in chronic hepatitis but there are no previous reports assessing the value of this parameter in studies of the equivalent condition in dogs. The authors examined samples from 39 dogs with histologically confirmed cases of idiopathic canine chronic hepatitis and showed that elevated total serum bilirubin was negatively associated with mean survival time. 

Multivariate analysis identified ascites as another negative prognostic factor, while increased bodyweight was also associated with early deaths, possibly due to the effect of the ascites. 

Journal of Veterinary Diagnostic Investigation 26 (2): 246-251.

Serial viscoelastic and traditional coagulation testing in equine gastrointestinal disease 

Kira Epstein and others, University of Georgia

Horses with gastrointestinal disease have a high incidence of abnormalities in both coagulation and brinolysis. The authors compared the results of thromboelastography (with and without tissue factor activation), Sonoclot coagulation analysis and traditional coagulations panels in 121 emergency admissions for gastrointestinal disease. 

Horses with gastrointestinal disease had dynamic changes in coagulation and brinolysis during the first four days of hospitalisation that were correlated with disease category, systemic inflammatory response syndrome, complications and fatalities. However, the observed changes in the particular laboratory parameters investigated were small and may have only moderate predictive value. 

Journal of Veterinary Emergency and Critical Care 23 (5): 504-516.

Use of a real-time PCR assay in controlling an outbreak of bovine ephemeral fever 

Deborah Finlaison and others, Department of Primary Industries, Narellan, New South Wales

Bovine ephemeral fever is a mosquito- borne viral disease of cattle in subtropical and temperate areas of Australia, Asia, the Middle East and Africa. Until recently, its diagnosis relied on clinical signs and relatively slow serological testing. 

The authors describe the application of a real- time polymerase chain reaction assay during an outbreak in New South Wales and northern Victoria in 2009- 10. They conclude that the test offers veterinarians and cattle owners rapid confirmation of infection within one to two days and provides real-time information about the presence of disease in a district. 

Australian Veterinary Journal 92 (1-2): 24-27.

Comparison of methods for bronchoalveolar lavage fluid collection in dogs

Katharine Woods and others, University of Guelph, Ontario

Bronchoalveolar lavage is a minimally invasive method for evaluating the main airways in patients with chronic cough, pulmonary neoplasia or unexplained abnormalities on thoracic radiographs. 

The authors compare the appearance of fluid obtained by manual aspiration with a hand-held syringe to that obtained by suction pump aspiration. In 13 healthy dogs examined under general anaesthesia, the suction pump aspiration method resulted in a significantly higher percentage of fluid retrieval and samples with a higher total nucleated cell count than the manual technique. 

American Journal of Veterinary Research 75 (1): 85-90.

Detection of prion protein in retina tissue samples in sheep and cattle

Jodi Smith and Justin Greenlee, National Animal Disease Center, Ames, Iowa

Conventional tests for diagnosing transmissible encephalopathies in livestock involve immunohistochemical or Western blot analysis of abnormal prion proteins in brain tissue. Taking post-mortem samples from the retina may offer potential advantages in easier access and in minimising risk of exposure to contaminated material for those collecting the samples. 

The authors compared the results of enzyme immunoassay examinations of retinal tissue from sheep with experimentally induced TSEs with those from standard assays. Their findings suggest that retina samples may be a useful method for rapid screening of animals with neurological signs suggestive of TSEs. 

American Journal of Veterinary Research 75 (3): 268-272.

Study on a rapid test for anticoagulant rodenticide poisoning in dogs

Stephanie Istvan and others, North Carolina State University

Anticoagulant rodenticide toxicosis is a major cause of morbidity and mortality in small animals. The authors assessed a point-of-care lateral ow analyser for the detection of various rodenticide compounds. Serum samples from a healthy dog spiked with one of six different compounds were tested and the results interpreted by three observers. 

There was complete agreement between the three on their findings. But while the assay detected warfarin at concentrations below the manufacturers’ recommended limit of detection, it was unable to detect any of the other and more commonly used second generation anticoagulant rodenticides.

Journal of Veterinary Emergency and Critical Care 24 (2): 168-173.

Skin surface sampling methods in canine superficial bacterial pyoderma

Philippa Ravens and others, Small Animal Specialist Hospital, North Ryde, NSW

Superficial bacterial pyoderma is a common secondary complication in various canine skin diseases. It is usually diagnosed by visual examination of cutaneous lesions or the results of impression smears. Bacterial culture is often considered to have limited additional diagnostic value but may be useful in guiding antimicrobial therapy. 

The authors compared results from three skin surface sampling methods – a dry cotton swab, a saline-moistened swab and skin surface scraping – together with the antimicrobial sensitivity of isolates from 27 dogs with CSBP. The staphylococcal isolates obtained were all susceptible to common empirical antimicrobials. Each sampling method produced similar results and may be equally suitable for obtaining samples for culture.

Australian Veterinary Journal 92 (5): 149- 155.

Evaluation of an angiotensin I and II rapid pressor response test in healthy cats 

Amanda Erickson Coleman and others, University of Georgia

Agents that blockade the renin- angiotensin-aldosterone system are used as treatments for systemic arterial hypertension. Exogenous angiotensin challenge with continuous blood pressure measurement is a commonly used method in human medicine for evaluating potential drug candidates. The authors investigated an angiotensin I and II rapid pressor response test in healthy cats. 

They found that this test elicited dose-dependent, transient increases in systolic and diastolic blood pressure and report that it has potential as a means of objectively evaluating the efficacy of various modifiers of the RAAS in cats. 

American Journal of Veterinary Research 74 (11): 1,392-1,399.