Can lupus anticoagulant be positive despite a normal aPTT?

How often does this occur and does this lower your suspicion for a "true" or clinically significant lupus anticoagulant?

1 Answer

Mednet MemberInvited Expert

Medical Oncology · Mayo Clinic Jacksonville

Answered on

aPTT is one of the assays that may be abnormal in the presence of lupus anticoagulant, but not always. Usually, when screening for lupus anticoagulant, there will be a "special" aPTT assay used that is a bit more sensitive to detect lupus anticoagulant. There are several different aPTT-based assays in use to screen for lupus anticoagulants with somewhat different sensitivities.

But given that an aPTT-based assay may not always be abnormal in the presence of lupus anticoagulant, guidance from the Scientific and Standardization Committee for Lupus Anticoagulant/Antiphospholipid Antibodies of the International Society on Thrombosis and Haemostasis (Devreese et al., PMID 33462974) recommends always checking two assays based on different principles for lupus anticoagulant detection. The first one is DRVVT-based assays, and the second one is an aPTT-based assay. These are multi-step assays, requiring mixing steps if screening tests are prolonged and then confirmatory testing.

So, not infrequently when screening for antiphospholipid antibody syndrome with a lupus anticoagulant test, one assay will be positive, while the other one may be negative (Moore et al., PMID 37597725).

I would not exclude the possibility of the presence of lupus anticoagulant with a normal aPTT.