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Hematology USMLE Step 3 > Section 4: Coagulation Disorders > Flashcards

Section 4: Coagulation Disorders Flashcards

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USMLE® Step 1 flashcards
1
Q

State the normal values of:

  1. Bleeding time
  2. Prothrombin time (PT)
  3. Partial thromboplastin time (aPTT)
A
  1. 2-7 min
  2. 12-14 sec
  3. 25-40 sec
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2
Q

List the platelet type bleeding

A
  • Petechiae
  • Epistaxis
  • Purpura
  • Gingiva
  • Gum
  • Vaginal

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5522-5532). Kaplan Publishing. Kindle Edition.

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3
Q

List the factor type bleeding

A
  • Hemarthrosis
  • Hematoma

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5522-5532). Kaplan Publishing. Kindle Edition.

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4
Q

What is the pathogenesis of the bleeding in von Willibrand Disease?

A

Platelet dysfunction

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5506-5512). Kaplan Publishing. Kindle Edition.

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5
Q

True or False:

The platelet count is normal in VWD

A

True

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6
Q

Why is the aPPT elevated in some 50% of patients with VWD?

A

The aPTT can be elevated in up to 50 percent of patients with VWD, because VWF deficiency destabilizes factor VIII.

A case of VWD is likely to present with epistaxis and/ or petechiae.

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5506-5512). Kaplan Publishing. Kindle Edition.

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7
Q

What is the best initial test whenever there is a platelet-type bleeding but the platelet count is normal?

A

Bleeding time

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8
Q

Most accurate test in VWD

A

Ristocetin cofactor assay and von Willebrand’s factor (VWF) level

If the level of VWF is normal, ristocetin testing will tell if it is working properly

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5513-5520). Kaplan Publishing. Kindle Edition.

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9
Q

VWD

Best initial therapy

Alternative if BIRx does not work

A
  • Desmopressin or DDAVP. This will release subendothelial stores of VWF and factor VIII, which will stop the bleeding
  • Factor VIII replacement. Factor VIII replacement has both VWF and factor VIII.

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5513-5520). Kaplan Publishing. Kindle Edition.

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10
Q

Diagnosis:

  • Platelet type bleeding
  • Platelet count <50,000
A

Idiopathic thromcytopenic purpura

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11
Q

Diagnostic tests in ITP

A
  • Antiplatelet antibodies
  • Sonogram: To assess for normal spleen size found in ITP
  • Bone marrow: To find increased numbers of megakaryocytes
  • Antibodies to the glycoprotein IIb/ IIIa receptor

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5537-5551). Kaplan Publishing. Kindle Edition.

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12
Q

A generally healthy patient comes with epistaxis and petechiae. No spleen is felt on examination. The platelet count is 24,000. What is the next step in management?

a. Prednisone
b. Bone marrow biopsy
c. Antiplatelet antibodies
d. Sonogram
e. Hematology consultation

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5537-5551). Kaplan Publishing. Kindle Edition.

A

A. Prednisone is the most important thing to do first in mild ITP. The main point of most ITP questions is that initiating therapy is more important than determining a specific diagnosis, particularly since ITP is a diagnosis of exclusion. All of the answers listed would be given on a CCS case at the same time. In a single best answer case, however, the most important thing is to start therapy.

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5537-5551). Kaplan Publishing. Kindle Edition.

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13
Q

A patient comes in with ITP and a platelet count of 5,000. The patient has epistaxis and petechiae as well as an intracranial hemorrhage and melena. What is the best initial step?

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5552-5575). Kaplan Publishing. Kindle Edition.

A

IVIG administration. The fastest way to raise the platelet count with ITP is to use intravenous immunoglobulins (IVIG) or RhoGAM. IVIG is the answer when the platelet count is low (< 20,000) and the case describes life-threatening bleeding, such as that into the bowel or brain. Transfusing platelets is wrong; this adds fuel to the fire and will likely make the situation worse.

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5552-5575). Kaplan Publishing. Kindle Edition.

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14
Q

ITP Rx under the following conditions:

  1. Platelet count > 50,000
  2. Platelet count < 50,000 with minor bleeding
  3. Platelet count < 20,000 with serious bleeding
  4. Recurrent episodes
  5. No rsponse to Rx (4) above
A
  1. No treatment
  2. Prednisone
  3. IVIG or Rhogam (Rho[D] immune globulin)
  4. Splenectomy
  5. Romiplostim and eltrombopag

Romiplostim and eltrombopag treat chronic ITP. They directly stimulate megakaryotes. Romiplostim and eltrombopag are thrombopoietin analogs

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5552-5575). Kaplan Publishing. Kindle Edition.

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15
Q

Diagnosis:

  • Normal platelet count
  • Platelet-type bleeding
  • Renal failure
  • Normal ristocetin test and VWF level

Best initial therapy?

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5579-5587). Kaplan Publishing. Kindle Edition.

A

Uremia-Induced Platelet Dysfunction. Uremia by itself prevents platelets from working properly; they do not degranulate

Desmopressin (DDAVP)

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5579-5587). Kaplan Publishing. Kindle Edition.

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16
Q

Relevance of mixing study in bleeding disorders

A

Mixing study is the first test to determine the difference between a clotting factor deficiency and a factor inhibitor antibody.

The aPTT will correct to normal with a clotting factor deficiency.

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5579-5587). Kaplan Publishing. Kindle Edition.

17
Q

List the diagnosis, best initial diagnosis, most accurate test and treatment based on the following presentation:

Joint bleeding or hematoma in a male child

A

Factor VIII deficiency

Mixing study

Factor VIII level

Severe deficiency: (< 1% activity): Factor VIII replacement; Minor deficiency: DDAVP

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5589-5619). Kaplan Publishing. Kindle Edition.

18
Q

List the diagnosis, best initial diagnosis, most accurate test and treatment based on the following presentation:

Joint bleeding or hematoma

A

Factor IX deficiency (less common than Factor VIII deficiency)

Mixing study

Factor IX level

Factor IX replacement

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5589-5619). Kaplan Publishing. Kindle Edition.

19
Q

List the diagnosis, best initial diagnosis, most accurate test and treatment based on the following presentation:

Rare bleeding with trauma or surgery

A

Deficiency of Factor XI

Mixing study

Factor XI level

Fresh frozen plasma (FFP) with bleeding episodes

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5589-5619). Kaplan Publishing. Kindle Edition.

20
Q

Rx for factor XII deficiency

Best initial test

Most accurate test

A

None

Mixing study

Factor XII level

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5589-5619). Kaplan Publishing. Kindle Edition.

21
Q

A woman presents with bleeding into her thigh after minor trauma. The aPTT is prolonged, and the prothrombin time is normal. Mixing study does not correct the aPTT to normal. What is the diagnosis?

A

Factor VIII antibody is the most common cause of a prolonged aPTT and bleeding that does not correct with a mixing study.

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5589-5619). Kaplan Publishing. Kindle Edition.

22
Q

Heparin induced thrombocytopenia (HIT)

Define HIT

Causes

CF

A

HIT presents with a drop in platelets (at least 50 percent) a few days after the start of heparin. This can be from any amount of heparin, no matter how small, because HIT is an allergic reaction.

Both unfractionated and low molecular weight heparin

Thrombosis is the most common clinical manifestation. Venous thromboses are 3 times more common than arterial thromboses

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5621-5631). Kaplan Publishing. Kindle Edition.

23
Q

HIT

Best initial diagnostic tests

Rx

A

The best initial diagnostic tests are:

  • Platelet factor 4 antibodies; or
  • Heparin-induced, antiplatelet antibodies

Treatment Best initial therapy:

  • Stop the heparin and use a direct thrombin inhibitor, such as argatroban or lepirudin.

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5621-5631). Kaplan Publishing. Kindle Edition.

24
Q

True or False:

If HIT happens with IV unfractionated heparin, it is ok to switch to low molecular weight heparin

A

False

25
Q

List the diagnosis, best initial diagnosis, most accurate test and treatment based on the following presentation:

  • Venous thrombosis
  • Elevated aPTT
  • Normal PT
  • Spontaneous abortion
  • False positive VDRL
A

Lupus anticoagulant or anticardiolipin antibodies

Mixing study

Russel viper venom test

Heparin followed by warfarin

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5635-5661). Kaplan Publishing. Kindle Edition.

26
Q

List the diagnosis, best initial diagnosis, most accurate test and treatment based on the following presentation:

Skin necrosis with use of warfarin

A

Protein C deficiency

Protein C level (MAT)

Heparin followed by warfarin

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5635-5661). Kaplan Publishing. Kindle Edition.

27
Q

List the diagnosis, best initial diagnosis, most accurate test (MAT) and treatment based on the following presentation:

Most common cause of thrombophilia

A

Factor V Leiden mutation

Factor V mutation test (MAT)

Heparin followed by warfarin

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5635-5661). Kaplan Publishing. Kindle Edition.

28
Q

List the diagnosis, best initial diagnosis, most accurate test and treatment based on the following presentation:

No change in the aPPT with a bolus of IV heparin

A

Antithrombin deficiency

Level of antithrombin III

Large amounts of heparin or direct thrombin inhibitor followed by warfarin

Fischer, Conrad (2012-09-22). Master the Boards: USMLE Step 3 (Kaplan Medical Usmle Master the Boards Step 3) (Kindle Locations 5635-5661). Kaplan Publishing. Kindle Edition.

29
Q

True or False:

Bleeding in the brain or the gastrointestinal system can
be from either platelet or clotting factor deficiency.

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 232). Kaplan Medical Test Prep. Kindle Edition.

A

True

30
Q

A 23-year-old woman comes to the emergency department with markedly increased menstrual bleeding, gum bleeding when she brushes her teeth, and petechiae on physical examination. Physical examination is otherwise normal. The platelet count is 17,000/μL. What is the most appropriate next step in therapy?

a. Bone marrow biopsy
b. Intravenous immunoglobulins
c. Prednisone
d. Antiplatelet antibodies
e. Platelet transfusion

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 232). Kaplan Medical Test Prep. Kindle Edition.

A

C. The bleeding in this case is mild, meaning there is no intracranial bleeding or major GI bleeding, and the platelet is not profoundly low. Prednisone is the best initial therapy. Initiating prednisone is more important than checking for increased megakaryocytes or the presence of antiplatelet antibodies, which is characteristic of ITP.

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 232). Kaplan Medical Test Prep. Kindle Edition.

31
Q

Vaccinations to give before a splenectomy

A
  • Neisseria meningitis
  • Haemophilus influenzae
  • Pneumococcus
32
Q

List the risk factors for DIC

A
  • Sepsis
  • Burns
  • Abruptio placentae or amniotic fluid embolus
  • Snake bites
  • Trauma resulting in tissue factor release
  • Cancer

There is bleeding related to both clotting factor deficiency as well as thrombocytopenia

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 234). Kaplan Medical Test Prep. Kindle Edition.

33
Q

List the diagnostic tests in DIC

A
  • Elevation in both the PT and aPTT
  • Low platelet count
  • Elevated d-dimer and fibrin split products
  • Decreased fibrinogen level (it has been consumed)

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 234). Kaplan Medical Test Prep. Kindle Edition.

34
Q

Rx of DIC

A

If platelets are under 50,000/μL and the patient has serious bleeding, replace platelets as well as clotting factors by using FFP

Heparin has no definite benefit.

Cryoprecipitate may be effective to replace fibrinogen levels if FFP does not control bleeding.

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 235). Kaplan Medical Test Prep. Kindle Edition.

35
Q

Which is the only thrombophilia important to test for with
first clot

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 235). Kaplan Medical Test Prep. Kindle Edition.

A

Antiphospholipid (APL) syndrome

36
Q

True or False:

APL is the one most likely to need lifelong warfarin
with only one clot.

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 235). Kaplan Medical Test Prep. Kindle Edition.

A

True

37
Q

True or False:

Do not transfuse platelets into those with HIT
because it may worsen the thrombosis.

Fischer, Conrad (2012-11-01). Master the Boards USMLE Step 2 CK (Page 235). Kaplan Medical Test Prep. Kindle Edition.

A

True

38
Q

A 28-year-old woman of Chinese descent is evaluated in the office for a diagnosis of right lower-extremity deep venous thrombosis during the 30th week of her first pregnancy. She took oral contraceptives for several years. Her medical and family history is otherwise noncontributory.

On physical examination, the patient is pregnant. There is painful swelling of the right leg from the ankle to the knee. The remainder of the examination is normal.

Laboratory studies, including complete blood count, prothrombin time, and activated partial thromboplastin time, are normal. Heparin and warfarin are begun.

Which of the following is the most appropriate next diagnostic test?

A Factor V Leiden and prothrombin G20210A mutational analysis
B Lupus anticoagulant and cardiolipin antibody measurement
C Protein C, protein S, and antithrombin measurement
D No further testing

A

Answer and Critique (Correct Answer = D)

This patient requires no further diagnostic tests at this time. Although pregnancy increases the risk for venous thromboembolism, testing for the presence of a hereditary thrombophilic disorder or markers of the antiphospholipid antibody syndrome (i.e., lupus anticoagulant and cardiolipin antibody concentration) does not alter the initial management or the duration of anticoagulant therapy in such patients. The factor V Leiden and prothrombin G20210A mutations are the most common mutations predisposing to venous thrombosis in white populations; they are, however, rarely found in native Asian and black populations. Although this patient does not have a family history of venous thrombosis, there is a small chance that she has an antithrombin, protein C, or protein S deficiency; however, pregnancy reduces the levels of protein C and S and their plasma levels are also depressed by oral anticoagulants. If follow-up testing is deemed appropriate, it will need to be postponed until after discontinuation of warfarin and completion of the pregnancy.

Key Points

  • Factor V Leiden and prothrombin G20210A mutations are the most common mutations predisposing to venous thrombosis in white populations, but are rare in Asian and black populations.
  • Levels of protein C and protein S are reduced during pregnancy and while taking oral anticoagulants, making testing for deficiency unreliable during these times.

Bibliography

Lim W, Eikelboom JW, Ginsberg JS. Inherited thrombophilia and pregnancy associated venous thromboembolism. BMJ. 2007;334:1318-21. [PMID: 17585161] [PubMed]

Hematology USMLE Step 3 (4 decks)

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