Prolonged APTT before cholecystectomy: mixing study interpretation and perioperative plan
A 67-year-old woman with symptomatic gallstones is admitted for elective laparoscopic cholecystectomy. Pre-operative tests show APTT 58 s (reference 25–35), PT 12.4 s (11–14), platelets 245 × 10^9/L and fibrinogen 3.2 g/L. She has no bruising or bleeding, no personal or family history of bleeding, and a dental extraction five years ago was uneventful despite a documented 'unexplained prolonged APTT'. Eight years ago she had a popliteal DVT after knee replacement and stopped warfarin three years ago. A 1:1 mixing study with normal plasma remains prolonged immediately (54 s) and after two hours at 37 °C (51 s). Factor assays: VIII 34%, IX 62%, XI 58%, XII 70%. The surgeon wants two units of fresh frozen plasma 'to be safe' and asks whether the operation should be cancelled; the anaesthetist is concerned about both bleeding and thrombosis. The theatre list is full and the case is scheduled for the next morning.
1. Interpret the mixing study and factor results. What is the likely diagnosis?
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The mixing study fails to correct at both the immediate and the two-hour incubation stages, which indicates an inhibitor rather than a factor deficiency. A specific factor VIII inhibitor is the first thought, but the pattern does not fit: her factor VIII is only modestly reduced (34%), she has no bleeding history, and factors IX, XI and XII are also mildly low. That combination is typical of a lupus anticoagulant, in which antiphospholipid antibodies interfere with phospholipid-dependent clotting assays and artificially lower several factor levels, most often VIII, IX, XI and XII.
A true mild haemophilia A with factor VIII 34% would correct on mixing and would be associated with a lifelong bleeding tendency, which her uneventful dental extraction argues against. A true acquired factor VIII inhibitor usually gives factor VIII below 10% with severe bleeding.
Confirm with a dilute Russell viper venom time (screen and confirm) and, if available, a dilute PT, together with anticardiolipin and anti-β2-glycoprotein I antibodies. Repeat at least 12 weeks apart to classify antiphospholipid syndrome. Her prior unprovoked? (post-operative) DVT is relevant: if the antibody profile persists, she has thrombotic risk, not a bleeding diathesis.
2. Do you give FFP, cancel surgery, or proceed? Give your perioperative plan.
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Do not give fresh frozen plasma, and do not cancel surgery solely because of the APTT. FFP will not reliably correct the phospholipid interference responsible for the prolonged APTT, exposes her to transfusion-associated circulatory overload, TRALI and thrombosis, and is not indicated in a patient with no bleeding history. The APTT here is not a measure of her bleeding risk.
Proceed with laparoscopic cholecystectomy, and document the reasoning in the notes and in a telephone discussion with the surgeon and anaesthetist. Perioperative plan: mechanical thromboprophylaxis plus low-molecular-weight heparin at prophylactic dose, balancing the history of previous DVT against the low bleeding risk of laparoscopic surgery; check renal function and platelet count before dosing. Do not give platelet transfusions or cryoprecipitate. If unexpected bleeding occurs, manage surgically and reassess rather than reflexively transfusing. Repeat coagulation testing is not needed for theatre clearance.
If she were later confirmed to have antiphospholipid syndrome with thrombosis, long-term anticoagulation and avoidance of oestrogen would become relevant, but that decision belongs to haematology and does not block this operation.
3. How would you exclude mild haemophilia A or a true factor VIII inhibitor, and what would change your management?
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Mild haemophilia A is excluded by the lack of any bleeding history, the normal dental extraction, the failure to correct on mixing and the involvement of multiple factors. If doubt remains, a chromogenic or two-stage factor VIII assay and a repeat sample in a different laboratory can resolve assay interference. A true acquired factor VIII inhibitor is excluded by the factor VIII level of 34% rather than <10%, the absence of bleeding and a negative Bethesda assay; if the Bethesda assay were positive, immunosuppression and postponement of surgery until the inhibitor is controlled would be required.
Management would change in three situations. First, if factor VIII were confirmed below about 20% with a bleeding phenotype, treat with factor VIII concentrate (or a bypassing agent for an inhibitor) rather than FFP, and delay elective surgery. Second, if a high-titre specific inhibitor were present, elective surgery should be deferred and haematology should direct haemostatic and immunosuppressive therapy. Third, if lupus anticoagulant were confirmed on two occasions with positive anticardiolipin or anti-β2GPI and a history of thrombosis, she would need long-term anticoagulation and a thrombosis-aware perioperative plan. None of these applies to the current numbers.