Lipid class composition and heparin sensitivity in the activated partial thromboplastin time

Area of Science:

• Biochemistry
• Hematology
• Clinical Chemistry

Background:

• Activated partial thromboplastin time (APTT) reagents are crucial for monitoring unfractionated heparin therapy.
• Variability in APTT reagent composition, particularly phospholipid content, contributes to inconsistent heparin sensitivity.
• Phosphatidyl serine (PS) is a key phospholipid component influencing APTT test performance.

Purpose of the Study:

• To evaluate the role of phosphatidyl serine (PS) concentration in APTT reagents on heparin sensitivity.
• To investigate the impact of lipid concentration and unsaturation on APTT test performance.
• To identify strategies for developing more reliable APTT reagents for heparin monitoring.

Main Methods:

• Preparation of APTT reagents with varying concentrations of purified phosphatidyl serine (PS).
• Assessment of heparin sensitivity and procoagulant activity across a range of lipid concentrations.
• Evaluation of phosphatidyl inositol (PI) as a PS substitute and the effect of liposome unsaturation.

Main Results:

• Decreased PS concentration in APTT reagents enhanced heparin sensitivity but reduced procoagulant activity.
• Total lipid concentration below 30 mg/l became rate-limiting, increasing heparin sensitivity alongside decreased procoagulant activity.
• Phosphatidyl inositol (PI) was not an effective substitute for PS, and lipid unsaturation had no significant effect.

Conclusions:

• Critical appraisal of phospholipid components, especially PS, is essential for improving APTT reagent reliability in heparin control.
• Optimizing PS levels and total lipid concentration can lead to more consistent and accurate heparin monitoring.
• This research facilitates the development of standardized APTT reagents, reducing inter-reagent variability in heparin sensitivity.