The physician has ordered several laboratory tests to help diagnose an infant’s bleeding disorder. Which of the following tests, if abnormal, would the nurse interpret as most likely to indicate hemophilia?
A. Bleeding time
B. Tourniquet test
C. Clot retraction test
D. Partial thromboplastin time (PTT)
Correct Answer: D. Partial thromboplastin time (PTT)
PTT measures the activity of thromboplastin, which is dependent on intrinsic clotting factors. In hemophilia, the intrinsic clotting factor VIII (antihemophilic factor) is deficient, resulting in a prolonged PTT. The PTT could be as prolonged as 2 to 3 times the high normal range. Once PTT is found to be prolonged, it should be followed by a mixing study. In a mixing study, the PTT should normalize if factor deficiency is suspected.
Option A: Bleeding time reflects platelet function. Bleeding time is a clinical laboratory test performed to evaluate platelet function. It involves the creation of a standardized incision and timing the cessation of bleeding. The historical indications were the pre-operative assessment of patients taking aspirin or NSAIDs and screening for von-Willebrand disease.
Option B: The tourniquet test measures vasoconstriction and platelet function.
The tourniquet test is part of the new WHO case definition for dengue. The test is a marker of capillary fragility and it can be used as a triage tool to differentiate patients with acute gastroenteritis, for example, from those with dengue.
Option C: Clot retraction test measures capillary fragility. All of these are unaffected in people with hemophilia. Clot retraction is a process driven by outside-in signaling by platelet integrin ?IIb?3 that results in the contraction of the fibrin mesh. The contraction of the fibrin clot results in the blood clot becoming smaller and excess fluid is extruded.
No comments:
Post a Comment