Assessing and treating disorders of primary hemostasis
Red blood cells in a fibrin clot.
History and physical examination
The history and physical examination are imperative to guide the differential diagnosis and focus the laboratory assessment. Conduct a full mucocutaneous survey to search for signs of platelet dysfunction, and carefully assess the patient for hepatosplenomegaly, lymphadenopathy, and/or signs of thrombosis because the presence of these abnormalities influences the workup. Inquire about easy bruising or excessive bleeding, determine the location and duration of bleeding and whether it occurs spontaneously or after trauma (immediate vs delayed), and assess for evidence of volume loss or anemia. Extensive bruising or bruising in unusual locations where trauma is less likely (trunk, inner arms, thighs) is suspect. Obtain previous platelet counts if possible to determine if the level is stable or decreasing. An acute drop in the platelet count of >50%, even if the count is still within normal range, may herald a severe disorder and requires close follow-up.2 Lifelong bleeding or a family history of a bleeding disorder may indicate a familial or congenital disorder. Congenital platelet defects are strongly associated with consanguinity. Bleeding should not be overlooked in the elderly because age-related changes in hemostasis parameters (shortened bleeding time and PTT; increased levels of factors II, VIII, and X; and decreased levels of antithrombin III) favor thrombosis, not bleeding. Aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and anticoagulants are common causes of bleeding or factors that exacerbate bleeding in the elderly. Clinicians may use a validated, objective bleeding score, such as the one derived from the Condensed MCMDM-1 VWD Bleeding Questionnaire,3 which grades the worst episode for each of the following: epistaxis; cutaneous manifestations; bleeding from minor wounds or the oral cavity; gastrointestinal bleeding; bleeding following tooth extraction or surgery; menorrhagia; postpartum hemorrhage; muscle hematoma; hemarthrosis; and CNS bleeding.4,5 The higher the bleeding score, the greater the likelihood of a bleeding disorder. In von Willebrand disease (vWD), the most common bleeding disorder, a score >4 has a sensitivity of 100% and a specificity of 87%, with a positive predictive value of 0.2.5 Uneventful molar tooth extraction is unlikely in a patient with a severe bleeding disorder.6
Assess for past medical history and for underlying diseases or their risk factors, particularly the following:
- Autoimmune and connective tissue disorders: systemic lupus erythematosus, rheumatoid arthritis, antiphospholipid syndrome
- Blood disorders and/or malignancy: leukemia, lymphoma, myeloproliferative disorders
- Infections: human immunodeficiency virus (HIV) infection; hepatitis A, B, or C; disease caused by cytomegalovirus; other viral or rickettsial disease
- Recent vaccinations; medication use (prescribed, over-the-counter, and alternative medications)
- Pregnancy status, recent transfusion, surgery or organ transplant
- Recent travel (malaria, rickettsial infection, leptospirosis, dengue or viral hemorrhagic fever)
- Alcohol and drug use, liver or kidney disease
A variety of infections may induce thrombocytopenia via immune-mediated platelet destruction, bone marrow suppression, or platelet consumption. In many viral infections (eg, rubella; mumps; varicella; infection with parvovirus, Epstein-Barr virus, or cytomegalovirus), thrombocytopenia is an incidental finding and spontaneously resolves with recovery. In some chronic infections, however, such as those caused by Helicobacter pylori, HIV, or hepatitis C virus (HCV), the thrombocytopenia may persist.2 Adults with the new onset of isolated thrombocytopenia should be screened for these chronic conditions. In many vector-borne diseases (eg, malaria, babesiosis, brucellosis, and anaplasmosis), thrombocytopenia is part of the clinical constellation, and parasites may be seen on peripheral blood smear.
Clinicians should know the mechanism and duration of action of common medications that affect platelet function. Aspirin irreversibly inactivates cyclooxygenase in platelets, and the effect lasts for the lifetime of the platelets. Bleeding time generally normalizes within 3 days after the discontinuation of aspirin. NSAIDs competitively inhibit cyclooxygenase, and the effect is related to the drug half-life, usually 1 day. Clopidogrel irreversibly inhibits the P2Y12 ADP receptor on platelets, impairing the activation of platelets and cross-linking of fibrin. The bleeding time gradually returns to baseline within about 5 days after the discontinuation of clopidogrel. Anticoagulants (heparin, warfarin, dabigatran, apixaban, rivoraxaban) and antiplatelet agents increase the tendency for bleeding and impair hemostasis at sites of hemorrhage. This is particularly important in the management of victims of head trauma. A strong index of suspicion is required in managing mild head trauma in patients treated with anticoagulants to minimize the risk for missed intracranial bleeding.