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Coagulation Profile Cobalamin 1325

Coagulation Profile
VetBooks.ir Definition Causes of Abnormally High Levels Drug Effects

Series of tests designed to assess the coagula- • Prolonged PT: extrinsic (factor VII) or Increased: warfarin toxicity, anticoagulant drugs
tion pathway and localize specific disorders of common coagulation (X, V, II, thrombin, and (e.g., heparin, factor Xa inhibitors)
coagulation factors that result in hemostatic fibrinogen) pathway defect; most sensitive
defects. Consists of prothrombin time (PT), test of anticoagulant rodenticide intoxication; Lab Artifacts
activated partial thromboplastin time (aPTT), vitamin K deficiency/antagonism, decrease/ Increase: inadequately filled tubes (causes
and sometimes activated clotting time (ACT). absence of extrinsic or common pathway specimen dilution by anticoagulant); traumatic
factors, disseminated intravascular coagula- venipuncture
Synonym tion (DIC), antiphospholipid antibodies,
Clotting profile antibodies to coagulation factors, biliary Specimen Collection and Handling
obstruction, liver failure Citrated plasma (blue top tube) for PT and
Physiology • Prolonged aPTT: defects in intrinsic pathway aPTT. Fill tubes completely, refrigerate, send
PT, aPTT, and ACT are tests that help (factors XII, XI, IX, VIII); hemophilia, severe to lab on ice. Commercial ACT tube (various
evaluate key coagulation factors that make von Willebrand disease (von Willebrand available) test performed in clinic.
up the coagulation cascade. Coagulation factor is carrier protein for factor VIII),
factors are a cascade of enzymes requiring DIC, vitamin K antagonism or absence, Relative Cost: $$
sequential activation. They eventually convert bile insufficiency, infiltrative bowel disease,
fibrinogen to fibrin, stabilizing the platelet exocrine pancreatic insufficiency, or liver Pearls
plug. The coagulation cascade is divided into failure • A coagulation profile is indicated if the
overlapping intrinsic, extrinsic, and common • Prolonged ACT: any disorder that sufficiently patient is bleeding into muscles or joints,
pathways. Activation of the extrinsic pathway increases PT, aPTT, or both (common has unexplained bleeding into body cavities,
is through tissue thromboplastin (released from pathway), marked thrombocytopenia or develops hematomas after blood draw.
cell surface membranes of injured tissues), and • A coagulation profile is indicated before liver
the intrinsic pathway is initiated by contact Next Diagnostic Steps to Consider biopsy.
activation of injured vessel basement membrane if Levels are High • ACT is a poorly sensitive point-of-care test
by negatively charged surfaces of collagen or Platelet count, fibrin degradation products, that should be followed up with PT and
platelets. specific factor analysis aPTT.
See pp. 431, 433, and 1202. • Low PT, aPTT, ACT values are not reliable
Reference Interval to detect a procoagulant or thrombogenic
• ACT: specific for tube/activator used Important Interspecies Differences state.
• aPTT: typically 8.6-12.9 seconds (dogs) and Factor XII deficiency will cause markedly
13.7-30.2 seconds (cats) prolonged aPTT without hemorrhage in cats. AUTHOR: Deborah G. Davis, DVM, DACVP
• PT: typically 5.1-7.9 seconds (dogs) and EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
Laboratory Tests
8.4-10.8 seconds (cats)

Cobalamin

Definition Reference Interval or insufficiency of IF in giant schnauzers,
Water-soluble vitamin with a porphyrin ring • Dogs: 250-910 ng/L; cats: 290-1500 ng/L border collies, other canine breeds, and rarely
• Unit conversion: 1 pg/mL = 0.1 ng/dL; cats; small intestinal bacterial overgrowth
Synonyms 1 pg/mL × 0.7378 = pmol/L (intestinal dysbiosis) as enteric bacteria bind
Cyanocobalamin, vitamin B 12 cobalamin.
Causes of Abnormally High Levels
Physiology Uncommon; dietary supplementation and Next Diagnostic Steps to Consider
Source is dietary. Released from food during possibly hepatocellular necrosis if Levels are Low
gastric digestion and bound to R-proteins. Rule out artifact due to sample light exposure.
Transferred to intrinsic factor (IF) in alkaline Next Diagnostic Steps to Consider Assess for intestinal diseases and for exocrine
intestinal pH. IF is produced by gastric parietal if Levels are High pancreatic insufficiency (serum trypsin-like
cells in dogs and by the exocrine pancreas in Review oral or parenteral supplements; assess immunoreactivity).
dogs and cats; it enhances ileal cobalamin for hepatic disease.
absorption. Cobalamin has hepatic storage. It Drug Effects
is a required cofactor in pathways involving Causes of Abnormally Low Levels Oral or parenteral supplements increase
folate and formation of succinyl coenzyme Decreased absorption due to ileal diseases concentration.
A. If the latter is impaired by cobalamin such as inflammation, villous atrophy,
deficiency or decreased intracellular availability, neoplasia; decreased IF production due to Lab Artifacts
methylmalonic acid accumulates, and defective gastric disease in dogs and exocrine pancre- • Falsely decreased by excessive light exposure
formation of neuronal lipids causes neurologic atic insufficiency in dogs and cats; congenital • Assays for human samples are unreliable in
disease. hypocobalaminemia due to malabsorption dogs and cats.

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