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Question 5: What advise would you give your surgical colleagues as a response to the hematology consultation? See answers overleaf. Hematology Quiz.
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Oman Medical Journal 2009, Volume 24, Issue 2, April 2009
PT โ 10.8s (9.3 โ 11.7) aPTT โ 51s (27.2 โ 39.1) Fibrinogen โ 3.0g/L (1.5 โ 4.2) Thrombin Time โ 15s (12 - 16) Question 1: The attending surgeon requests a hematology consultation before surgery regarding the prolonged aPTT. What is your response? (Case continues): The Corrected aPTT: 37.5s (Normal plasma is added to the test (patientโs) plasma in a 50:50 mix and the aPTT is repeated) Question 2: What can you infer from the results of the mixing test? Question 3: Will you do any more laboratory test before responding to your colleague in surgery? (Case continues): The following are the results of intrinsic pathway coagulation factor assays: Factor VIII โ 89% Factor IX โ 78% Factor XI โ 72% Factor XII- 15% Question 4: Why did you carry out the intrinsic pathway factor assays? Question 5: What advise would you give your surgical colleagues as a response to the hematology consultation? See answers overleaf
Al-Yahyai M, et al. OMJ. 24, 145-146 (2009); doi:10.5001/omj.2009.
Oman Medical Journal 2009, Volume 24, Issue 2, April 2009 From the Department of Hematology and Blood Tranfusion, Royal Hospital, Muscat, Sultanate of Oman. Received: 23 Dec 2008 Accepted: 10 Feb 2009 Address correspondence and reprint request to: Dr. Maha Said Al-Yahyai, Department of Hematology and Blood Tranfusion, Royal Hospital, Muscat, Oman. E-mail: [email protected] Answer 1: I would repeat the aPTT to confirm that it is a true result and if still prolonged. I would also do a mixing tests. (correction tests) Answer 2: The prolongation of the aPTT was caused by a coagulation factor deficiency. On adding the normal plasma in a 50:50 volume mix and repeating the aPTT, the test is verified because the deficient coagulation factor level is brought up to more than 30%, which is adequate to normalize the aPTT^1. If an inhibitor to a coagulation factor was present, the mixing tests will not correct the aPTT to the normal range as the inhibitor will prevent the action of whatever coagulation factor is added to the mixture. Hence, we know that the prolonged aPTT was caused by a coagulation factor deficiency and NOT an inhibitor. Answer 3: Yes, I would:
The parts of the coagulation cascade tested by the Prothrombin time(PT) activated partial thromboplastin time (aPTT) and the thrombin time (TT) which are the coagulation screening tests used in clinical practice. Answer 5: The patient has a factor XII deficiency. He also has a family history of Factor XII deficiency. Three factors were considered to confirm the presence of a factor deficiency. (1) An abnormal laboratory result, confirmed to be true after repetition of the test. (2) A past family history of bleeding (3) Bleeding after surgical challenge/child birth/tooth extraction. The patient had a confirmed low factor XII. A positive family history and no past personal history of bleeding as Factor XII deficiency does not cause bleeding. It is safe to proceed with the surgery. The patient does not need any blood products or factor concentrates to tide over surgical challenge as Factor XII deficiency is not known to cause bleeding. Other causes of an isolated prolonged aPTT^3