Which factor may interfere with the activated protein C resistance (APCR) screening test?

The activated protein C resistance (APCR) screening test assesses the functionality of the protein C pathway, which is crucial for controlling coagulation and preventing excessive clotting. The presence of a lupus anticoagulant can significantly interfere with this screening test. Lupus anticoagulants are antibodies that target phospholipids and can cause hypercoagulability and prolong the activated partial thromboplastin time (aPTT), leading to false positive or misleading results in the APCR test. This can result in an inaccurate assessment of a patient's risk for thrombotic events.

In contrast, conditions such as protein C deficiency, antithrombin deficiency, and protein S deficiency typically do not interfere directly with the APCR test itself. Instead, they may present issues related to the coagulation pathway but do not create the misleading results associated with the presence of lupus anticoagulants. Therefore, understanding how lupus anticoagulants affect the APCR screening is essential for accurate diagnosis and subsequent management of thrombotic risks.