Why they did it
The lack of specificity of prolonged coagulation screening tests such as prolongation of prothrombin time (PT) and activated partial thromboplastin time (APTT) has made specific point-of-care testing for the presence of anticoagulant rodenticides desirable.
What they did
Sixty milliliters of blood was obtained from a healthy dog with no history of a bleeding abnormality and a normal PT. The separated serum was mixed with analytical grade methanol then divided into equal aliquots to which a known concentration of each anticoagulant (warfarin, pindone, chlorophacinone, brodifacoum, bromethalin, and desmethylbromethalin) was added to create varying concentrations of each. Bromethalin and desmethylbromethalin are not anticoagulants but were included for specificity. Unaltered serum and serum mixed with analytical grade methanol were used as controls. All samples were tested according to the manufacturer’s instructions for the test kit (Rodenticide-Stx Poison Test, Kacey Diagnostics), which is labeled to detect warfarin, and interpreted by three individuals blinded to compound identity.
What they found
The test only indicated a positive result for the presence of warfarin, and the negative controls yielded a negative result. Interpretation by all three test readers was identical.
The authors acknowledge possible study limitations such as the use of a single canine donor or possible instability in the stock solutions.
While the test was easy to use and did not result in any false positive results, the test did not detect three of the four rodenticides tested even in samples that were more than six times the manufacturer’s stated level of detection. The usefulness of this test is limited to its label claims of detecting warfarin.
Istvan SA, Marks SL, Murphy LA, et al. Evaluation of a point-of-care anticoagulant rodenticide test for dogs. J Vet Emerg Crit Care 2014;in press.
Link to article: http://onlinelibrary.wiley.com/doi/10.1111/vec.12140/abstract 
Jennifer L. Garcia, DVM, DACVIM, is a veterinary internal medicine specialist at Sugarland Veterinary Specialists in Houston, Texas.