Hematology (MoD) Flashcards by Charles Shirley

Normal hemoglobin, hematocrit ranges?

Hemoglobin: 12-14 for women, 14-16 for men
Hematocrit: 36 to 50%

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Where is iron absorbed?

Proximal duodenum

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Anemia of chronic disease pathogenesis

Inflammatory mediators (Il-6) lead to incr. hepcidin, in turn leading to decreased Erythropoietin

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Iron deficiency lab fidnings

Nonspecific, but:
• On CBC: RBC count, H/H low, low MCHC
• Anisocytosis (hypochromia, microcytosis, causes incr. RDW)
• Poikilocytosis (elliptical cells, target cells)

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Large, hypersegmented (>5 lobes) neutrophils on a peripheral blood smear…

Megaloblastic anemia

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Megaloblastic anemia peripheral blood smear characteristics

Large hypersegmented (> 5 lobes) neutrophils is the most important characteristic, but also: pancytopenia, large hyper chromic oval RBCs, hyperlobated megakaryocytes (platelet precursors)

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Where is vitamin B12 absorbed

Terminal ileum

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What is pernicious anemia? Cause and symptoms?

Specific form of megaloblastic anemia caused by autoimmune destruction of gastric parietal cells with Ab to intrinsic factor; large, smooth, beefy, red tongue, also CNS subacute degradation (differentiates from folate deficiency)

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Where is folate absorbed

Proximal jejunum

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Where does folate come from in diet?

Green vegetables (poor storage so need to replenish constantly)

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Where does vitamin B12 come from in diet?

Animal products (strict vegetarians at risk of deficiency)

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4 things can cause folate deficiency

Decr. intake (e.g. alcoholism, poor diet, infarct), impaired absorption (e.g. intestinal disease), incr. requirement (e.g. cancer), incr. utilization (e.g. methotrexate)

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Serum labs increased by B12 deficiency?

Homocysteine, methylmalonic acid (MMA)

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Diseases associated with aplastic anemia

Fanconi anemia, paroxysmal nocturnal hemoglobinuria (also whole body irradiation but that’s less important)

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Diseases associated with pure red cell aplasia

Neoplasia, parvovirus infection, collagen vascular disease, blackfan-diamond syndrome

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Haptoglobin function

Bind free hemoglobin

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Danger of free heme in bloodstream

Kidney damage

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Difference between sickle cell disease and hemoglobin C?

In sickle cell disease mechanism is substitution of glutamic acid with valine at 6th position of beta globin chain; for hemoglobin C substitution is lysine instead of valine

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“Target cells”

One of: thalassemia, poikilocytosis or liver disease

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What is the Mentzer index and what is it used for?

MCV/RBC ratio; distinguish thalassemia from iron deficiency (less than 13 thalassemia, greater than 13 iron deficiency)

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Why isn’t alpha thalassemia (generally) more severe than beta?

Because beta and gamma globulin chains are more soluble than alpha so hemolysis and ineffective erythropoiesis less pronounced

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Test used to diagnose hereditary spherocytosis

Osmotic fragility test (spherocytes are more osmotically fragile)

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What causes intermittent anemia

G6PD deficiency (leads to decr. NADPH, thus decr. glutathione activity, thus reduced ability to handle oxidative stress); also remember pyruvate kinase deficiency causes continuous anemia

Peripheral smear findings in G6PD deficiency

Heinz bodies, bite cells

Mechanism behind and most important test used to diagnose paroxysmal noctural hemoglobinuria

RBCs lack proteins necessary to prevent complement-mediated lysis; flow cytometry (demonstrates reduced CD55 and CD59)

Difference in mechanisms underlying warm antibody HA and cold agglutinin HA?

In warm Ab HA, IgG binds to RBCs which are then phagocytksed by splenic macrophages; in cold agglutinin HA IgM binds RBCs, then fixes complement

Diseases associated with cold agglutinin HA

B cell neoplasms and infections (esp mycoplasma pneumoniae)

Universal RBC donor type

O-

Universal plasma donor type

AB+, AB-

Presumed effect of "one unit" of blood on an "average" patient

Incr. Hgb by 1 gm/dL and Hct by 2-3%

Presumed effect of "one unit" of fresh frozen plasma

Incr. any factor level by 2-3%

For what reason is irradiation performed (with regards to transfusion)? What samples do not need to be irradiated

Prevent GVHD (in the immunocompromised, hematologic disorders, intrauterine transfusions and Hodgkin's disease); FFP, cryoprecipitate/coagulation factors

Possible metabolic complications of transfusion

Citrate toxicity, hyperkalemia, hypothermia, volume overload

Platelet's delta (dense) granule contents

ATP, ADP, serotonin, ca++

Platelet's alpha granule contents

PF4, PDGF, P-selectin, platelet fibrinogen, VWF, thromboglobulin, thrombospondin

Where is GP IIb/IIIa found and what is it?

Platelets; receptor for VWF and fibrinogen

What is GP Ib/V/IX and where is it found?

Receptor for VWF; platelets

How is VWF crucial for both primary and secondary hemostasis?

Binds collagen to platelets in primary hemostasis, binds to factor VIII (thus stabilizing it) in secondary hemostasis

ADAMTS13 function

Metalloprotease that lyses VWF (don't want it to be active forever, only large multimers have hemostatic activity)

What form of VWF has hemostatic activity?

Only the large multimers

Plavix (clopidogrel) mechanism of action

ADP receptor inhibitor (ADP activates platelets)

Bernard-Soulier syndrome underlying mechanism

Deficiency in Ib (Ib/V/IX)

Glanzmann thrombasthenia underlying mechanism

Deficiency in IIb/IIIa compromises fibrinogen cross linking

Cause and symptoms of thrombotic thrombocytopenic purpura

Loss of ADAMTS13 causes ultra-large VWF multimers, leading to widespread platelet activation and microvascular thrombosis; classic pentad - fever, thrombocytopenia, microangiopathic HA, mental status changes, renal failure

Bacterium associated with Hemolytic Uremic Syndrome

E coli (specifically d/t shiga-toxin)

Test used to diagnose antiphospholipid syndrome?

dilute Russell Ciper Venom test (dRVVT), also remember aPTT can be elevated but it isn't a bleeding disorder

Underlying mechanism behind Heparin-induced thrombocytopenia

Antibodies to PF4+ heparin lead to platelet activation and microvascular occlusion

Fibrinogen factor number

Factor I

Prothrombin factor number

Factor II

What factor deficiencies do NOT cause bleeding

XII, prekallikrein, HMWK

Intrinsic, extrinsic, common pathway factors

Intrinsic: HMWK, prekallikrein, VIII, IX, XI, XII Extrinsic: VII, Tissue factor Common: I, II, V, X

Describe the role of platelets in secondary hemostasis

PF3 present on activated platelets, plays a role in the activation of factors IX, X, prothrombin

What clotting factors are vitamin K dependent? How so?

II, VII, IX, X, S, C; necessary for carboxylation of gamma carbon of glutamic acid of Glands domain (remember ca++ crucial for this process)

What factors does thrombin play a role in activating?

I, V (leads to more thrombin), VIII, XI (positive feedback on intrinsic pathway), XIII (cross-links/stabilizes fibrin)

TFPI action

Blocking extrinsic pathway by compromising interaction of TF with factor VII

Heparin mechanism of action

Inactivates IIa

Disseminated intravascular coagulation labs

Incr. PT, PTT, TT Decr. fibrinogen and platelets Incr. FSP D-dimers