Problems by using whole blood in heparin measurements

Area of Science:

• Hematology
• Clinical Chemistry

Background:

• Whole blood (WB) is often used for coagulation testing, but its use in heparin measurements presents challenges.
• Packed cell volume (PCV) and platelet Factor 4 can influence WB assay results.
• Standard coagulation assays may exhibit variable accuracy and precision with WB due to heparin response differences.

Purpose of the Study:

• To investigate the suitability of various coagulation assays for heparin measurements using whole blood (WB).
• To evaluate the impact of packed cell volume (PCV) on WB heparin assays.
• To determine the most accurate and precise method for WB heparin testing.

Main Methods:

• Comparison of recalcification time (RT), activated partial thromboplastin time (APTT), and thrombin clotting time (TCT) using WB and plasma.
• Assessment of WB stability within 1 hour for heparin measurements.
• Correlation analysis between TCT results from WB (T20) and plasma (T30).

Main Results:

• WB must be used within 1 hour due to platelet Factor 4 influence.
• Increasing PCV moderately affected Ca++ levels and assay results.
• RT and APTT showed low accuracy and precision with WB due to variable heparin response.
• TCT demonstrated high accuracy and precision in plasma and showed good correlation (r=0.89) with WB T20 results.

Conclusions:

• Thrombin clotting time (TCT) is a reliable and accurate method for heparin measurements in whole blood (WB).
• The TCT method for WB correlates well with plasma-based TCT, making it a viable alternative.
• Calcium thrombin clotting time (CaTCT) is not recommended for whole blood heparin assays.