Page 2675 - Cote clinical veterinary advisor dogs and cats 4th

Prothrombin Time (PT) Pyuria 1377

blood from a compressible vein (e.g., limb) Lab Artifacts Pearls
in patients with suspected/confirmed bleeding Citrate (blue top) tube must be filled to capacity PIVKA test may be slightly more sensitive than
VetBooks.ir Important Interspecies Differences Specimen Collection and Handling vitamin K–dependent disorders. For example,
prothrombin time, but it is not specific for
or the results will be falsely prolonged.
tendencies.
it can be prolonged with DIC or inherited
Cats with hepatic, biliary, or inflammatory
collected in citrate (blue top tube). Spin and
bowel diseases can have prolonged results Plasma from minimally traumatic venipuncture factor VII deficiency.
without bleeding tendencies. separate plasma. Refrigerate specimens that will AUTHOR: Deborah G. Davis, DVM, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
be analyzed within 3 hours; freeze if > 3 hours.
Drug Effects
Prolonged results: vitamin K antagonists (e.g., Relative Cost: $$
warfarin, heparin) and antimicrobials (gut
sterilization causing vitamin K deficiency)

Prothrombin Time (PT)

Definition defects in extrinsic or common pathway (factors Specimen Collection and Handling
Screening coagulation test of the extrinsic and VII, X, V, II, and I), heparin, presence of fibrin Citrated plasma (blue top tube). Avoid trau-
common coagulation pathways degradation products (FDPs), antibodies to matic venipuncture (can artifactually prolong
phospholipids or coagulation factors PT). Fill tube to capacity without overfilling.
Synonyms Immediately mix the blood and anticoagulant
One-stage prothrombin time (OSPT), PT Next Diagnostic Steps to Consider by repeated gentle inversion.
if Levels are High
Physiology Rule out causes (p. 433); specific coagulation Relative Cost: $$
2+
Plasma is warmed and mixed with a Ca - factor assays are rarely done.
thromboplastin reagent, allowing tissue factor Pearls
in the reagent to activate factor VII in the Causes of Abnormally Low Levels • Antagonism or absence of vitamin K–
plasma. This initiates the extrinsic and common • PT may be shortened (due to high fibrino- dependent coagulation factors, as occurs
coagulation pathways. The resulting fibrin clot gen) with inflammation. Decreased PT does in anticoagulant rodenticide intoxication,
is detected by an instrument. The prothrombin not indicate hypercoagulability; rather, it is warfarin treatment, or hepatic disease,
time (PT) is the time from the plasma and usually a result of suboptimal phlebotomy tends to increase PT before activated partial
reagent mixing to the formation of the clot. (sample collection artifact). thromboplastin time (aPTT). This is due to
the short half-life of factor VII.
Reference Interval Drug Effects • Prolonged PT and normal aPTT can be seen
Values are approximate (reference intervals are Therapeutic Coumadin/warfarin should prolong in cats with DIC. Dogs with DIC can have Laboratory Tests
laboratory and instrument specific). Dogs: 7-11 PT by 1.5- to 2.5-fold, and vitamin K 1 should normal PT.
seconds; cats: 5-8 seconds. return it to normal.
AUTHOR: Deborah G. Davis, DVM, DACVP
Causes of Abnormally High Levels Lab Artifacts EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
Hepatic disease, vitamin K deficiency or antago- Improper blood/citrate ratios impact results
nism, disseminated intravascular coagulation (too little blood can prolong, and too much
(DIC), anticoagulant intoxication, hereditary blood can shorten PT).

Pyuria

Definition Identification of leukocytes in urine is per- Causes of Abnormally High Levels
Increased numbers of leukocytes, specifically formed through microscopic evaluation of the • Neutrophils: cystitis/pyelonephritis, urinary
in the urine secondary to urogenital tract urine sediment. Results are recorded as number tract neoplasia, urolithiasis, contamination
inflammation of leukocytes per 40× objective (hpf). Individual from the genital tract
leukocytes cannot be identified on wet mount • Lymphocytes: polypoid cystitis, lymphoma
Synonym cytology preparations alone; staining of urine • Eosinophils: drug-induced acute tubulointersti-
Leukocyturia either through Sedi-Stain™ or Romanowsky tial nephritis; polypoid or eosinophilic cystitis
stains is necessary.
Physiology Next Diagnostic Steps to Consider
Leukocytes migrate from the blood to the Reference Interval if Levels are High
urinary tract secondary to inflammation Healthy patients have < 5 leukocytes/hpf. Ensure sterile collection of urine. Exclude
from infectious or noninfectious etiologies. urinary tract infection by submitting sterile

www.ExpertConsult.com