A quantitative, semi-automated and computer-assisted test for lupus anticoagulant

Area of Science:

• Hematology
• Clinical Chemistry
• Immunology

Background:

• Lupus anticoagulants (LA) are antiphospholipid antibodies associated with thrombosis.
• Accurate quantification of LA is crucial for risk assessment and patient management.
• Existing LA detection methods may lack standardization or quantitative capabilities.

Purpose of the Study:

• To design and validate a quantitative assay for lupus anticoagulants (LA).
• To adapt the Activated Partial Thromboplastin Time (APTT) and Russell Viper Venom Time (RVVT) for LA quantification.
• To establish a reproducible and sensitive method for measuring LA levels.

Main Methods:

• Developed a quantitative LA test using APTT and RVVT, incorporating low and high cephalin concentrations.
• Calculated the Lupus Ratio (LR) by comparing patient plasma clotting times to normal plasma.
• Utilized an automated clot timer and computer program for LR calculation and standard curve generation (log-logit model).

Main Results:

• Established reference ranges for the LR in 150 healthy individuals, defining the Lupus Anticoagulant Unit (LA-U).
• Demonstrated comparable sensitivity to the Kaolin Clotting Time (KCT).
• Showed differential results for specific patient groups: negative in warfarin, positive in heparin, negative in Factor V/VIII/IX deficiency, and mixed results with Factor VIII inhibitors.

Conclusions:

• The APTT and RVVT can be effectively adapted for quantitative LA measurement.
• The developed assay is simple, reproducible, and offers high sensitivity and specificity for LA quantification.
• This quantitative approach provides a valuable tool for clinical assessment of LA-positive patients.