Mixing studies for lupus anticoagulant: mostly yes, sometimes no

Area of Science:

• Clinical Immunology
• Hematology
• Laboratory Medicine

Background:

• Lupus anticoagulants (LAs) are key indicators of antiphospholipid syndrome (APS).
• APS is linked to adverse outcomes, notably thrombosis and pregnancy complications.
• Current LA diagnostics primarily rely on clot-based assays, including Russell viper venom time (RVVT) and activated partial thromboplastin time (APTT).

Purpose of the Study:

• To evaluate the role and necessity of mixing studies in lupus anticoagulant (LA) identification.
• To discuss the varying recommendations for mixing studies in recent LA testing guidelines.
• To present a viewpoint on when mixing studies may be omitted in the LA diagnostic algorithm.

Main Methods:

• Review of current LA testing methodologies, focusing on clot-based assays (RVVT, APTT).
• Analysis of recommendations from major guidance documents regarding LA identification and exclusion.
• Discussion of the function of mixing studies in differentiating LA activity from other coagulation inhibitors.

Main Results:

• All recent LA testing guidelines recommend RVVT and APTT assays.
• Mixing studies are generally supported by guidelines for LA identification/exclusion.
• There is variability in guidelines regarding the specific application and importance of mixing studies.

Conclusions:

• Mixing studies are typically essential for the accurate identification and exclusion of lupus anticoagulants.
• However, there are specific circumstances where omitting mixing studies may be appropriate.
• Further clarification on the precise role and placement of mixing studies in diagnostic algorithms is warranted.