Lupus anticoagulant testing with optical end point automation.

Area of Science:

• Hematology
• Clinical Chemistry

Background:

• Lupus anticoagulant activity is screened using dilute Russell viper venom time and kaolin clotting time (KCT).
• Kaolin clotting time (KCT) has high turbidity, limiting its use in automated optical detection systems.
• There is a need for alternative lupus anticoagulant screening tests compatible with modern automation.

Purpose of the Study:

• To evaluate five recently reported screening tests as potential alternatives to the kaolin clotting time (KCT) for lupus anticoagulant detection.
• To assess the sensitivity, specificity, and compatibility of new assays with automated systems.

Main Methods:

• Evaluated silica clotting time, Textarin/Ecarin ratio, Taipan venom time, factor V ratio, and a low-turbidity kaolin clotting time.
• Compared the performance of these tests against KCT using lupus-positive and lupus-negative plasma samples.
• Assessed the impact of warfarin and heparin on the tested assays.
• Investigated phospholipid correction and anticardiolipin antibody positivity.

Main Results:

• Silica clotting time demonstrated comparable sensitivity and specificity to KCT, detecting 10/12 KCT-positive samples.
• Silica clotting time allows for confirmatory phospholipid correction but showed false positives in 2/15 warfarinized samples.
• Factor V ratio was unaffected by warfarin or heparin and identified 3 anticardiolipin-positive samples previously screened as lupus-negative.
• A combination of silica clotting time and dilute Russell viper venom time met requirements for sensitivity, phospholipid dependence, and automation compatibility.

Conclusions:

• Silica clotting time and dilute Russell viper venom time are suitable alternatives for lupus anticoagulant screening, offering automation compatibility and phospholipid dependence.
• The factor V ratio serves as a valuable secondary screening tool for anticoagulated patients and anticardiolipin antibody-positive individuals.