Background: Lupus Anticoagulant (LA) is a heterogeneous immunoglobulin that prolongs phospholipid-dependent coagulation tests, especially APTT-based. Prolonged PT is a less frequent presentation. The strong presence of LA is likely to give erroneous results in coagulation tests and factor measurements, that can be misleadingly interpreted as a coagulopathy. For bleeding risk assessment it is necessary to exclude congenital or acquired factor deficiencies. Despite of these laboratory findings, LA is associated with hypercoagulability and thrombosis.  

Aims: To report a case of a 71-year-old patient referenced to our hospital with a significant prolonged TP and APTT, for bleeding risk assessment pre-colonoscopy. The procedure, scheduled to investigate patient significant weight loss and anorexia, was postponed for intimidation regarding hemorrhage due to laboratory findings. The patient was clinically asymptomatic and stable, and no personal bleeding history was reported. Other clinical findings reported on Fig.1.

Methods: Laboratory investigation included Werfen® LA integrated tests (dRVVT and SCT), one-stage and chromogenic factor assays SIEMENS® and ROTEM Sigma® complete test.

Results: Preliminary laboratory investigation revealed a strong LA and factor deficiencies (Table1a). Most factor deficiencies were not confirmed when assayed at higher plasma dilutions (Table1b), with only FVII, FII and FXI slightly decreased (not justifying screening results prolongation). ROTEM Sigma® showed EXTEM and INTEM slight prolonged CT, probably in relation to LA, without any other abnormality in clot formation.

Conclusions: This case illustrates how the presence of a potent LA can interfere with factor assays interpretations, besides APTT. Significantly prolonged screening tests in a patient without bleeding symptoms, can make us suspect of LA and guide our investigation for a quicker response, mostly in situations when invasive procedure is needed and urgent.
In this context, instead of PT and APTT, viscoelastic tests may be a good strategy since it reflects more accurately and quickly patient coagulation status.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/unusual-laboratory-presentation-of-lupus-anticoagulant-prolonged-prothrombin-time-pt-and-activated-partial-thromboplastin-time-aptt-without-severe-factor-deficiency/