A simplified assay for the quantification of circulating activated protein C

Area of Science:

• Biochemistry
• Hematology
• Clinical Diagnostics

Background:

• Existing assays for activated protein C (APC) are often impractical for routine laboratory use due to time constraints or high detection limits.
• Measuring circulating APC is crucial for understanding hemostasis and thrombosis, particularly in conditions like venous thromboembolism (VTE).

Purpose of the Study:

• To develop and validate a simplified assay for measuring circulating activated protein C (APC).
• To assess APC levels in patients with venous thromboembolism (VTE) compared to healthy individuals using the new assay.

Main Methods:

• A novel assay was developed to measure both free in vivo APC and APC complexed with PC inhibitor (PCI).
• APC levels were measured in 339 plasma samples (165 VTE patients, 174 healthy controls) using both the new and a previous assay.
• Assay correlation and APC levels in VTE patients versus controls were statistically analyzed.

Main Results:

• The new assay demonstrated high correlation (r=0.954) with a previous assay, indicating equivalence.
• Mean APC levels were significantly lower in VTE patients (0.037±0.009 nM) compared to healthy individuals (0.041±0.010 nM).
• The new assay effectively measures total circulating APC, including free APC and APC-PCI complexes.

Conclusions:

• The developed simplified assay is equivalent to previous methods and suitable for routine laboratory diagnostics.
• Lower circulating APC levels are confirmed in VTE patients, highlighting the assay's clinical relevance.
• This assay facilitates broader clinical application for assessing APC levels and related thrombotic risks.