November 29, 2010

Q&A: Appropriate Testing for Platelet Abnormality

Easy bruising is a common complaint in medical practice for both primary care clinicians and hematologists. Easy bruising can be defined as bruising without a history of trauma or bruising after minor trauma that would not have caused bruising in the past. Differentiating between bruising that might be considered normal versus clinically significant is challenging given that there may not be specific symptoms and signs.

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This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Allergies, Blood & Immune System articles more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.
In this article:
Distinguishing pathologic versus benign bruising
MCQ: clinical scenario
MCQ: answer
MCQ: explanation

Distinguishing pathologic versus benign bruising

A bruise (ecchymosis) is a collection of blood beneath the skin resulting from extravasation of blood from surrounding vessels. Easy bruising can result from abnormalities affecting the blood vessels themselves, the surrounding skin and subcutaneous structures, platelet number and function, or coagulation cascade function.

The etiology of bruising can be broadly classified by the anatomic/physiologic defenses against bleeding. The following list includes the main categories with their most commonly associated etiologies:
  • Disorders of blood vessels and surrounding tissue (eg, physical abuse, vitamin C deficiency, connective tissue disease)
  • Platelet abnormalities (eg, drugs, systemic illness including infections, von Willebrand disease)
  • Coagulation disorders (eg, coagulation factor deficiency, liver disease, vitamin K deficiency)
As bruising is a common complaint, the clinician should be familiar with important symptoms and signs that require further workup. A lack of physical trauma related to a bruise raises suspicion of an underlying bleeding diathesis. However, this can sometimes be misleading. Some patients, particularly those who are fair skinned, overweight, and female, can develop bruising with minimal trauma and may not remember being injured.

Reassurance is appropriate for patients with bruising mainly on the distal lower extremities, no other evidence of bleeding, and no personal or family history of significant bleeding. These patients should be followed up with in a few months. For patients with recent medication exposure known to cause bruising or bleeding, the clinician should discontinue the culprit medication if possible. After allowing for drug washout and bruise healing (approximately two to four weeks), the clinician should reexamine the patient for evidence of new bruises. Patients with atypical bruising over the face, trunk, or back should be evaluated for physical abuse.

Patients with any of the following should be referred to a hematologist:
  • Continued significant bruising (five or more bruises greater than 1 cm in diameter) without any known trauma
  • Personal or family history of abnormal bleeding, especially after surgeries or injuries
  • Associated bleeding from other sites (eg, recurrent epistaxis, gingival bleeding, hemarthrosis)
  • Abnormal laboratory tests that suggest a bleeding diathesis

MCQ: clinical scenario

A patient with long standing renal insufficiency develops mild generalised ecchymoses. Platelet dysfunction is suspected despite a normal platelet count.

Which test would be most useful in this patient?

a) Bone marrow aspirate
b) Clot retraction
c) Tourniquet test
d) Bleeding time
e) Prothrombin time (PT)

MCQ questions & answers on medicalnotes.info

MCQ: answer

The correct answer is D

MCQ: explanation

Renal insufficiency is associated with a bleeding tendency. Hemorrhagic manifestations are usually mild (i.e., ecchymoses or purpura) but can be severe in occasional patients who may have gastrointestinal tract or intracranial bleeding. Modern techniques for the management of uremia have definitely reduced the incidence of severe bleeding episodes in patients with renal failure, but hemorrhages still represent a major clinical problem, particularly for patients undergoing surgery or invasive procedures.

The bleeding time is usually abnormal in congenital defects of platelet function such as Glanzmann's thrombasthenia. The bleeding time is frequently abnormal in acquired platelet function abnormality such as that seen in uremia and the myeloproliferative syndromes. The bleeding time is most helpful as an indicator of platelet abnormality, either in number or function. The bleeding time is usually normal when the platelet count is decreased but still more than 100,000/mm3 (100 × 109 /L). With platelet counts less than 100,000/mm3, there is a rough correlation between severity of thrombocytopenia and degree of bleeding time prolongation.

In uremia, there is frequently demonstrable abnormalities in platelet function tests but not sufficient to entirely explain bleeding problems. In addition, up to 50% of uremic patients develop some degree of thrombocytopenia.

Reference(s)
1). UpToDate: Easy bruising. Accessed ..20. Available online: https://www.uptodate.com/contents/easy-bruising

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