Page 2628 - Cote clinical veterinary advisor dogs and cats 4th

Factor Xa Inhibition Fecal Culture 1339

Drug Effects (green top tube) for 3-5 minutes for • Local hospitals may be able to perform this
Propylene glycol, glycerol, and ethanol can plasma. assay. The chemical detected is the same in
VetBooks.ir positive (Kacey). Relative Cost: $$$ AUTHOR: Erin N. Burton, DVM, MS, DACVP
both humans and animals.
interfere with these tests, resulting in a false-
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
Pearls
Specimen Collection and Handling
• Kacey: 20 mcL (1 drop) of plasma. Separate • Cats are more susceptible to ethylene glycol
0.5-1 mL of whole blood in an EDTA (lav- toxicity (minimum lethal dose = 1.4-6.6 mL/
ender top tube) or lithium heparin (green kg) than dogs (minimum lethal dose =
top tube) for 3-5 minutes for plasma. 4.4 mL/kg).
• Catachem: 0.1 mL of plasma. Separate • Gas chromatography is considered the gold
0.5-1 mL of whole blood in an EDTA standard, but is not always practical for
(lavender top tube) or lithium heparin clinical settings.

Factor Xa Inhibition

Definition plasma anti-Xa activity rather than traditional Relative Cost: Check with reference lab or
Inhibition of Factor Xa is the mechanism coagulation assays. Specific assays are required local human hospital labs.
for certain direct-acting oral anticoagulants for different drug (e.g., heparin, rivaroxaban)
(e.g., rivaroxaban, apixaban). The action monitoring. Pearls
of these drugs can’t be assessed by classical • PT may suffice for qualitative measurement
coagulation tests. Plasma concentration is the Reference Interval of patient clotting ability (i.e., clot intensity),
current method for evaluation for appropriate Send out test for veterinary reference lab; may but a drug-specific assay is needed for
therapeutic levels or overdose. have to use human lab or local human hospital monitoring and assessing blood levels.
• Thromboelastography may serve as an
Physiology Causes of Abnormally High Levels alternate means of assessing anticoagulation
Factor Xa inhibitors, used to control throm- Overadministration if Factor Xa inhibition assay is unavailable.
boembolic conditions, act directly without • These assays can also be used to assess the
needing cofactors for activation. Most of these Causes of Abnormally Low Levels efficacy of heparin anticoagulation.
drugs are up to 60% bioavailable in dogs. Underdosing
Therapeutic activity generally correlates with AUTHOR & EDITOR: Lois Roth-Johnson, DVM, PhD,
DACVP
plasma concentration. Classical coagulation tests Specimen Collection and Handling
Laboratory Tests Laboratory Tests
(PT, aPTT) do not correlate with blood levels. Plasma (green top tube), 1 mL minimum. Spin,
Therefore, monitoring is done by measuring collect plasma immediately and freeze.

Fecal Culture

Definition pathogens. Microbial susceptibility may also be Next Diagnostic Steps to Consider
Microbiologic evaluation of feces for growth provided. if Levels are Low
of enteric bacterial pathogens Intermittent shedding of pathogen may cause
Causes of Abnormally High Levels false-negative results. If clinical signs continue
Synonym Common small animal enteric pathogens to suggest enteric bacterial disease, consider
Stool culture include Salmonella spp, Shigella spp, Cam- PCR assay or repeat culture.
phylobacter spp, E. coli O157:H7, Clostridium
Physiology difficle, Yersinia spp. Culture results that include Drug Effects
Enteric dysbiosis and diarrhea in small animal normal enteric flora are not diagnostically Antimicrobial therapies, even low levels, may
may be caused by bacterial pathogens or useful. inhibit or alter culture growth.
pathobionts. Routine aerobic and anaerobic
cultures are often of limited utility in complex Next Diagnostic Steps to Consider Lab Artifacts
bacterial communities such as feces. Alternative if Levels are High False-negative:
culture techniques are often necessary for the See pp. 182, 260, and 898. • Pre-analytical error from delay in shipping
identification of enteric pathogens in fecal or setting up culture, omission of sus-
samples. Causes of Abnormally Low Levels pected fastidious organisms on submission
Growth may be absent despite infection, espe- form to guide laboratory personnel on
Reference Interval cially after antimicrobial therapy. Alternatively, appropriate media selection, inappropriate
Reported as negative or degree (light, the cause for signs may not be due to bacterial shipping media, and exposure of anaerobes
moderate, heavy) of growth of specific infection. to oxygen

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