Laboratory and Diagnostic Findings

Three tests are recommended for use in initial screening for possible bleeding disorders:14-16 activated partial thromboplastin time (aPTT), prothrombin time (PT), and platelet count (Fig. 25.4). If no clues are evident as to the cause of the bleeding problem and the dentist is ordering the tests through a commercial laboratory, an additional test can be added to the initial screen: thrombin time (TT).14-16 Patients with positive results on screening tests should be evaluated further so that the specific deficiency can be identified and the presence of inhibitors ruled out.

A hematologist orders these tests, establishes a diagnosis that is based on the additional testing, and makes recommendations for treatment of the patient who is found to have a significant bleeding problem. The screening laboratory tests are discussed in detail in Chapter 24. In patients with prolonged aPTT, PT, and TT, the defect involves the last stage of the common pathway, which is the activation of fibrinogen to form fibrin to stabilize the clot.

The plasma level of fibrinogen is determined, and if it is within normal limits, then tests for fibrinolysis are performed. These tests, which detect the presence of fibrinogen, fibrin degradation products, or both, consist of staphylococcal clumping assay, agglutination of latex particles coated with antifibrinogen antibody, and euglobulin clot lysis time.

Hereditary hemorrhagic telangiectasia is a disorder consisting of multiple telangiectatic lesions involving the skin and mucous membranes.6 Bleeding occurs because of the inherent mechanical fragility of the affected vessels.

Lastly comment

Problems with the construction of connective tissue components of the vessel wall are the underlying weakness in Ehlers-Danlos disease, osteogenesis imperfecta, pseudoxanthoma elasticum, and Marfan syndrome.6,10 Readers are referred to other sources for further information on these latter diseases

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