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Evaluation of a hemostatic disorder is commonly initiated when (1) a patient or referring physician suspects a bleeding tendency, (2) a bleeding tendency is discovered in one or more family members, (3) an abnormal coagulation assay result is obtained from an individual as part of a routine examination, (4) an abnormal assay result is obtained from a patient during preparation for surgery, or (5) a patient has unexplained diffuse bleeding during or after surgery or following trauma. Evaluation of a possible hemostatic disorder in each of these scenarios is a stepwise process that requires knowledge of the various classes of hemostatic disorders commonly found under the particular circumstances. The patient’s history, the results of physical examination, and an initial set of hemostatic tests usually enable a tentative diagnosis. However, more specific tests are commonly necessary to make a definitive diagnosis. This chapter reviews the necessary steps.


Hemostatic disorders can conveniently be classified as either hereditary or acquired (Table 6–1). Alternatively, hemostatic disorders can be classified according to the mechanism of the defect. Of the acquired disorders, the thrombocytopenias are the most frequently encountered entities. Thrombocytopenias can result from reduced production of platelets, excessive destruction caused by antibodies or other consumptive processes, or pooling of platelets in the spleen, as in hypersplenism (Chap. 7); however, if hypersplenism is the sole cause of a hemostatic disorder, it is rarely severe enough to cause pathologic bleeding.

Table 6–1.Classification of Disorders of Hemostasis

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