Mixing studies for lupus anticoagulant: does it matter how we mix?

Area of Science:

• Clinical Chemistry
• Hematology
• Immunology

Background:

• Lupus anticoagulant (LA) testing is essential for diagnosing thrombotic disorders.
• Standardized protocols for LA mixing tests are recommended, yet variations in normal pool plasma (NPP) sources persist.
• Differences in NPP composition may influence mixing study outcomes.

Purpose of the Study:

• To investigate the impact of different mixing media on lupus anticoagulant mixing test results.
• To compare the performance of commercial lyophilized NPP, commercial quality control plasma, and patient plasma as mixing media.

Main Methods:

• Forty-five remnant plasma samples were analyzed using Siemens Dade Actin FSL Activated PTT Reagent on a BCS XP analyzer.
• Four types of mixing media were used: standard human plasma, control plasma N, patient plasma with normal coagulation, and homemade normal pool plasma (NPP).
• Activated partial thromboplastin time (aPTT) values from mixing studies were compared across the different media.

Main Results:

• Median aPTT values for mixing studies using commercial lyophilized NPP, commercial quality control plasma, and patient plasma were comparable (26.6, 26.3, and 26.8 a s, respectively).
• A significantly higher median aPTT value (27.9 a s) was observed when using homemade NPP (P < 0.05).
• No significant differences were found between commercial NPP, control plasma, and patient plasma.

Conclusions:

• The choice of normal pool plasma (NPP) significantly impacts lupus anticoagulant mixing test results.
• Commercial lyophilized NPP is a reliable and consistent medium for LA mixing studies.
• Homemade NPP may introduce variability and is not recommended for LA mixing tests.