Exam 1 Flashcards
How does a refractometer work?
It bends the light passing through the fluid. Refractation is proportionate to the solute concentration.
Which solutes interfere with a refractometer’s readings?
Lipemia: chylomicrons, lipids
urea
glucose
cholesterol
How do you convert a leukocyte percentage into an absolute count?
Multiply the TNCC by the percentage of each leukocyte type
ex: TNCC= 10,000 ul, 80% of cells are segs, .80 x 10000 = 8000 segs/uL
Red Top tube
no anticoagulant, blood is expected to clot. Serum used for biochem profile
Red/Black tiger top
serum seperator, gel promotes blood clot formation and seperates cells from serum. Uses: chemistry analysis, serology
Purple top
EDTA, anti-coagulant, Ca chelator. Preserves cell morphology. Uses: cbc, fibrinogen, retic count, buffy coat analysis, fluid analysis, blood banks, Coombs test, PCR, endogenous ACTH
Green top
Heparin, anticoagulant- inhibits thrombin. Uses: chemistry panels, avian/reptile cbc, plasma colloid oncotic pressure (COPs), measurement of electrolytes, specific tests
Blue top
Citrate, anti-coagulant, Ca chelator. Uses: coag tests- PT, aPTT, FDP, PIVKA, antithrombin, coag factor analysis, von willebrand’s factor analysis
Gray top
sodium floride oxalate, anti-coagulant, Ca chelator. Inhibits glucose metabolism-> fluoride inhibits glycolysis. Uses: Plasma for serial glucose, lactate and pyruvate
Which tubes have a Ca2+ chelator?
Lavendar, Blue, Gray
What is a reference interval?
A reference interval describes fluctuation is a healthy population.
What percentage of the healthy population is included in a reference interval?
95%
What are the 3 phases during which errors occur?
Pre analytical, analytical, post- analytical
Which one is most common?
Pre analytical, analytical, post- analytical
pre-analytical
If an EDTA tube is not adequately filled, what changes to you see on the CBC?
Excess EDTA causes RBCs to shrink, will see decreased PCV and decreased MCV
Difference between sensitivity and specificity
Sensitivity: SNOUT! Helps rule out a dz when the result is negative
Specificity: SPIN! When a test is highly specific, a positive result means the patient most likely has the dz
What is the major regulatory hormone for thrombopoiesis?
Thrombopoetin
Where does TPO come from and how does it work?
It’s synthesized in the liver and kidneys. It stimulates platelet production.
What laboratory tests to we use to access platelet concentration?
evaluations of PLTs on a blood smear
hematology analyzer
When do you get falsely decreased platelet concentrations on the analyzer (2 instances)?
PLT clumps (cat and cattle), increased numbers of enlarged platelets
What laboratory tests to we use to access platelet morphology?
Blood smear
What does an increased MPV mean?
Mean Plt Volume, increased MPV suggests increased thrombopoesis
What does the presence of macrothrombocytes suggest?
Increased numbers of enlarged plts suggests active production of plts
What test is used in the clinical setting to evaluate platelet function?
Buccal mucosal bleeding time (BMBT)
What test do we use to access platelet production?
Bone Marrow Aspirate
What are your major mechanisms for thrombocytopenia?
Production, Destruction, Sequestration and Loss or Consumption
What are the 2 major mechanisms for thrombocytosis?
Increased production and increased distribution in the plasma
Increased production and increased distribution in the plasma
What are 3 diseases that may cause a reactive thrombocytosis?
chronic inflammatory dz (IL-6 stimulation), iron deficiency anemia, chronic hemorrhage, IMHA, some neoplasms
3 situations that cause thrombocytosis
Rebound from thrombocytopenia Response to some drugs (vincristine) Post-splenectomy Excitement and exercise (epinephrine) Splenic contraction
What is the mechanism involved in von Willebrand’s Disease (vWD)?
defect in adhesion molecule that binds PLTs during initiation of plt plug
re: vWB disease
What changes would you see on a CBC?
Would you see a change in the bleeding time?
PLT count would be normal
BMBT- prolonged
What test would you run to confirm vWD?
Analyze plasma for vWF
Which factor drives amplification? And which 4 factors does it affect?
Thrombin. Feeds back on to VII, XI, VIII and V
What cofactor is required for antithrombin to inactivate thrombin?
Heparin
What are the two major end-products of fibrinolysis?
Fibrin degradation products and D-dimers
How do you collect a sample for coagulation tests? What tube do you use?
• Clean stick in a sodium citrate tube (blue top), centrifuge, then send off citrated plasma (no rbc, wbcs or plts)
What are the 2 tests that access the intrinsic/common pathway? Which is more sensitive? How do you interpret these tests (e.g. when is it abnormal)?
• Intrinsic: aPTT and ACT
o aPTT measures time for fibrin clot formation in citrated plasma + contact activator. It requires 70% deficiency of factor before prolongation is detected. It’s more sensitive that ACT
• Extrinsic: PT
o PT measures time for fibrin clot formation in citrated plasma + tissue factor. Significance of prolongs time would be Factor VII deficiency, it would be a good test for vit k deficiency because of the short ½ like of factor VII
What is the 1 test that accesses the extrinsic/common pathway? How do you interpret this test?
• Thrombin Time
o Measures time for fibrin clot formation in citrated plasma + thrombin
o Significance of prolongation
Abnormalities of fibrinogen
Inhibitors of fibrin formation (eg heparin, FDPs)
What 2 tests do you use to access fibrinolytic activity? How do you interpret these tests?
• FDP: Inhibits platelet function and fibrin polymerization, ONLY when FDPs are pathologically increased
• D-dimers: Caused by plasmin degradation of crosslinked fibrin
o Increased concentration occurs with:
Increased fibrinolysis
Severe internal hemorrhage with fibrinolysis
Decreased clearance of FDP by liver
More specific than FDP
• What are the major coagulation factors involved in Warfarin toxicosis
II, VII, IX, X (1972!)
What is the mechanism that causes the coagulopathy in warfarin toxicosis?
o Normally there are 2 enzymes in the liver that help vitamin K donate electrons to factors. Warfarin inhibits vitamin K from borrow electrons and the enzymes don’t have a negative charge so they just go rolling by the plt.
Lab features of Warfarin toxicosis?
o PT prolonged
o aPTT, ACT prolongd
o PIVKA positive
o Plt count, usually normal
• What are the two phases of DIC?
o Hypercoagulable phase: thrombosis and ischemic necrosis and organ disfunction
o Consumptive phase: consumption of plts, coag factor and AT. Bleeding
• What are the laboratory features of the consumptive phase of DIC?
o Thrombocytopenia (mild-moderate) o Prolonged PT, aPTT o Decreased fibrinogen concentration o Increased FDP and D-Dimers o Decreased antithrombin (AT) o Hemorrhagic anemia o Schistocytes
What are the changes that occur in the coagulation factors in liver disease coagulopathy?
o Decreased synthesis of coag factors, production of dysfunction factors (failure to metabolize/reduce vitamin K)
If a patient has severe liver disease, what should ALWAYS be done prior to biopsy?
o Screen for coagulation abnormalities!
What is the classic presentation?
Young animal with a bleeding disorder
Hypochromic, microcytic, keratocyte RBCs are indicative of
iron deficiency anemia
The most common kind of non-regenerative anemia in domestic animals is
anemia of inflammatory dz
How do you calculate HCT
mcv x rbc / 10
Why would MCHC increase? Decrease?
Increases are artifactual (hemolysis, lipemia, etc)
Decreases usually due to presence of many reticulocytes that are still making hemoglobin
What is a left shift?
Increased concentration of immature neutrophils in the blood (usually bands)
Define leukemia
presence of neoplastic cells in the blood or bone marrow
Pelger Huet anomaly
inherited, results in neutrophil nuclei not segmenting, look band shaped. Looks like a severe left shift but the animal looks healthy
Birman Cat Neutrophil granulation anomaly
50 % Have granules in their neutrophils, no clinical sig
Chediak-Higashi Syndrome
Inherited anomaly where lysosome granules fuse, as well as melanin granules fuse (silver haircoat). Neutrophils don’t work as well and animals have a tendency to bleed
Stress Leukogram
lymphopenia
neutrophilia (can be 2x)
eosinopenia
Lack of stress response in a sick animal- think addisons
Inflammatory Leukogram
left shift or neutrophil concentration greater than 2x the upper limit of the reference interval
Excitement Leukogram
Lymphocytosis, no left shift. Seen often is cats
What are 3 things that can cause Neutropenia?
consumption within inflammatory lesion
immune mediated destruction
lack of production by bone marrow
What are 3 things that can cause lymphopenia?
steriod response
acute viral infections
immunodeficiency (rare)
2 things that cause monocytosis?
inflammation
stress response
2 things that cause eosinophilia?
parasitism
hypersensitivity
mast cell tumor
3 reasons for decreased production of plts ?
bone marrow hypoplasia
neoplasia
myelonecrosis/myelofibrosis
3 reasons for destruction of plts?
ITP Allimmune thrombocytopenia (rare) Modified live virus vx (don't vx before sx)
Reasons for sequestration/abnormal distribution of plts?
splenomagaly, splenic torsion, neoplasia
hepatomegaly, portal hyertension
vasodilation in endotoxic shock
severe hypothermia
Reasons for plt loss thrombocytopenia?
Hemorrhage
Alone doesn’t cause signifianct thrombocytopenia but severe acute causes mild thrombocytopenia
Reasons for plt consumption?
DIC
Vasculitis (ricketsial dz, FIP)
Viral infection
Reasons for secondary or reactive thrombocytosis?
chronic inflammatory disease
iron deficiency anemia
chronic hemorrhage
IMHA
What would the plt/coag evaluation look like for a pet with vWD
plt count- normal
BMBT- prolonged
ptt/act normal but can be prolonged if factor VII deficiency is pronounced
