Hemostasis
Causes of Abnormal Screening Results
Causes of Abnormal Screening Results | Specimen Collection and Transport Issues | Medication | Pathologic Conditions | Factor Deficiencies | Factor Inhibitors
In many cases, a clinician must deal with an extended PT or aPTT in a patient who is not receiving anticoagulant therapy. Often, the key to identifying the cause of this laboratory finding is knowledge of the patient's clinical history. These tests are commonly ordered as part of the diagnostic work-up of a patient with a history of bleeding. This clinical situation is significantly different from the patient with no history of bleeding who is tested prior to surgery to rule out possible coagulation defects. The aPTT, or the more sensitive aPTT-LA, can be ordered as part of an antiphospholipid syndrome work-up of a patient with a history of thrombosis or recurrent miscarriage. Three distinct test algorithms should be employed for these three very different clinical situations.
In order to choose an optimal diagnostic algorithm, one should understand the many potential causes of an abnormal screening test. In the absence of prescribed anticoagulant therapy, prolongation of these tests generally can be attributed to five common causes.
- Specimen Collection and Transport Issues
- Medication
- Pathologic Conditions
- Factor Deficiencies
- Factor Inhibitors
The following profiles are designed to assess the factors that may cause an extended screening test:
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