Hematologic Disorders Quiz

Thrombotic Thrombocytopenic Purpura (TTP) - Key Points

• Parenteral treatment should be administered subcutaneously or intravenously, not intramuscularly
• Intramuscular injections should be avoided in patients with coagulopathies to prevent hematomas
• Vitamin K administration takes 18–24 hours to have effect; fresh frozen plasma or prothrombin complex concentrate may be required for bleeding patients
• Patients with TTP exhibit systemic illness with classic manifestations including thrombocytopenia, microangiopathic hemolytic anemia, neurologic abnormalities, fever, and acute kidney injury
• TTP diagnosis requires thrombocytopenia and microangiopathic hemolytic anemia; neurologic abnormalities and acute kidney injury may also be present
• ADAMTS13 enzyme cleaves von Willebrand factor multimers; its deficiency leads to platelet aggregation and microcirculation clumping
• Reduced ADAMTS13 activity and positive anti-ADAMTS13 antibody test establish the diagnosis of TTP
• The "PLASMIC" score predicts the likelihood of finding low ADAMTS13 activity diagnostic for TTP
• Plasma exchange is the mainstay of TTP treatment, improving survival rates from 90% mortality to 90% survival
• Immunosuppressive drugs like prednisone or rituximab are used to reduce the production of anti-ADAMTS13 antibody
• Thrombotic Thrombocytopenic Purpura (TTP) should be treated when suspected, and a definitive diagnosis is not necessary to initiate treatment
• Liver disease-induced coagulopathy may present asymptomatically or incidentally on coagulation laboratory studies

Heparin-Induced Thrombocytopenia and Disseminated Intravascular Coagulation

• Heparin-induced thrombocytopenia (HIT) scoring system: 0-3 points indicate low probability, 4-5 points indicate intermediate probability, and 6-8 points indicate high probability.
• HIT antibodies were found in 0.9% of patients with low pretest probability, 11.4% in those with intermediate scores, and 34% in those with high scores.
• Heparin must be discontinued if HIT is suspected, and an alternative anticoagulant such as argatroban or fondaparinux should be started.
• Low-molecular-weight heparin should not be substituted, and warfarin should not be used until platelet count recovers.
• Anticoagulation should continue for 2-3 months.
• Patients with a history of HIT can be safely reexposed to heparin after a year, if necessary.
• Disseminated Intravascular Coagulation (DIC) presents as uncontrolled spontaneous diffuse bleeding in patients with severe illness.
• Conditions that cause DIC include trauma, advanced adenocarcinomas, obstetric crises, and acute promyelocytic leukemia.
• In some cases of DIC, clotting manifestations may predominate, leading to recurrent thrombosis without bleeding.
• Acute DIC is characterized by thrombocytopenia, prolongation of PT/INR and aPTT, reduction of plasma fibrinogen level, and increases in D-dimer and fibrin degradation products.
• D-dimer and FDP reflect fibrinolytic activity, and fibrinogen levels below 100 mg/dL may correlate with bleeding risk in DIC.
• Testing for DIC should include platelet count, PT/INR, aPTT, fibrinogen, and D-dimer.

Treatment of Thrombocytopenia and Heparin-Induced Thrombocytopenia

• Serologic studies are indicated if SLE, hepatitis C, or HIV infection is suspected.
• High-dose corticosteroid, such as prednisone or dexamethasone, is the initial treatment for all patients with thrombocytopenia.
• Patients who do not respond to corticosteroids or whose thrombocytopenia recurs when the corticosteroids are stopped may undergo splenectomy.
• In refractory cases of thrombocytopenia, other immunosuppressants may be used, such as rituximab, azathioprine, or cyclophosphamide.
• Thrombopoietin analogues such as romiplostim and eltrombopag have become more widely used for treatment of refractory cases of thrombocytopenia.
• Heparin-Induced Thrombocytopenia (HIT) is caused by the development of an antibody directed against a heparin-platelet factor 4 complex.
• HIT develops in about 5% of patients who receive heparin, with surgical patients at higher risk.
• HIT manifests between 5 and 10 days after starting any kind of heparin.
• Thrombosis develops in about 50% of patients who have HIT.
• The most sensitive, readily available screening test for HIT is an enzyme-linked immunosorbent assay (ELISA) for anti-PF4 antibody.
• A pretest probability scoring system (the 4“T’s”) has been validated for the diagnosis of HIT, considering thrombocytopenia, timing of platelet fall, and thrombosis or other sequelae.
• The platelet count does not usually drop below 50,000/mcL in HIT; a lower platelet count suggests another etiology.