HOW I DO – Surgical Clearance for High aPTT – PART – 9
HOW I DO – Surgical Clearance for High aPTT – PART – 9
(All the articles published in past are available at www.shyamhemoncclinic.com/blog/)
Question: In last part, we covered some important points related to surgical clearance for patients with low platelet count, or high PT. 1. Antiplatelet agents like Aspirin do NOT reduce platelet number. Only the function is reduced. 2. Bleeding risk requires evaluation of all pillars of hemostasis i.e. platelet count, coagulation tests like PT and aPTT, comorbidities like liver or kidney disease. Also, degree of abnormality e.g. mild versus severe thrombocytopenia. And type of procedure planned, such as high risk tissue like brain or spinal cord or eye; whethere it will be possible to apply pressure or not in case of bleeding; expertise of the person doing the procedure. 3. Vitamin k has a very limited role. It works only in vitamin k deficiency, and requires only 2 to 5 mg maximum to completely correct PT. Vitamin k deficiency is seen mostly in patients with prolonged hospitalization on broad spectrum antibiotics, rarely in other group of patients. 4. For patients with high PT, or liver disease, perioperative management is very complex. And must involve a hematologist as far as possible. Unless it is due to cirrhosis, where other experts may also be able to manage.
Last time, our conversation stopped at patients with high aPTT? How do we manage them?
Answer: Those with high aPTT mostly have a congenital bleeding disorder. Most common one being Hemophilia A, due to factor 8 deficiency. And Hemophilia B due to factor 9 deficiency. Other congenital disorders that lead to high aPTT are extremely rare. Even Hemophilia is a fairly uncommon disorder, and most people who come to you as adults are already aware of their diagnosis. Non Hemophilia disorders leading to high aPTT are extremely rare. Hence diagnosis must be made very carefully. Some of these patients have high aPTT but high thrombotic tendency, instead of bleeding tendency. Such as lupus anticoagulant, anti cardiolipin antibody, anti beta2 glycoprotein antibody.
Degree of aPTT does not always correlate well with bleeding severity. Hence if there is any prolongation of aPTT, it should be seriously evaluated. Many of the disorders that lead to high aPTT, cannot be managed adequately with few FFP. That makes it even more important to be certain about the diagnosis and have a plan in place before surgery.
Que: Thank you for stressing the importance of this. So, once the patient has high aPTT, what should be the next steps for diagnosis?
Ans: First and most important step is to repeat aPTT. aPTT is highly sensitive to analytical errors i.e. not enough sample, test done several hours after collection, issues with control sample, machine not calibrated well. Just a couple of days ago, I had a patient whose pre procedure test showed aPTT at 50 i.e. significantly high. Test was repeated by home collection by same lab. Again high. Adult patient with history of previous procedures, and no history of excess bleeding. I asked the patient to go to a specialty hematology lab personally, and give sample there for detailed evaluation. But the test turned out to be normal at the specialty lab. No further evaluation was required.
If it was abnormal, next test would have been a mixing study i.e. with half patient plasma and half control plasma. If this leads to correction of aPTT, patient requires further testing for factor deficiency. Most common being 8, and next common 9. If these are normal, then sequentially lab will test for other factors. If mixing study does not correct aPTT, that means patient has an inhibitor. Lab will then test for these e.g. lupus anticoagulant. Inhibitors, as discussed above, lead to prolongation of aPTT, but cause thrombotic tendency, rather than bleeding tendency.
Que: Very interesting. For all practical purposes, however, high aPTT means more complex evaluation and better refer to a hematologist.
Ans: Yes, and also understand the value of specialty hematology pathologist. These tests are very complex, and just buying machines does not work. Hence big laboratories are not necessarily good at these. They need to have pathologist and technician also who understand the field of coagulation. Once the factor deficiency is found, good laboratories don’t label it right away. They would frequently run the test again at least once, to ensure that result is consistent. Even at Albert Einstein College of Medicine, where I studied, protocol was same. For a lab that was a referral center for so many other laboratories, also would not believe their first report!! Sometimes, they would even ask for a repeat sample from the patient, and run all the tests again.
Reason I am highlighting this, is due to the fact that, many large laboratories, or hospital laboratories try to be comprehensive. Means they offer all the possible tests. Even if they don’t have, or if the right technician or pathologist has left, they rely on machines only. And continue to offer these tests. Unfortunately, this is true with many other tests which are highly dependent on human skills, even in this day and age of significant automation. But that is a different topic altogether – standardization of tests.
Basically, choose your lab carefully. And just as your excellent clinical specialist cannot be an expert in everything, your excellent pathologist is also not an expert in everything. Many subspecialities in pathology too!!
March 15th, 2025
Dr Chirag A. Shah; M.D. Oncology/Hematology (USA), 9998084001. Diplomate American Board of Oncology and Hematology. Ahmedabad. drchiragashah@gmail.com www.shyamhemoncclinic.com