Reproducibility and variability of activated clotting time measurements in the cardiac catheterization laboratory

Area of Science:

• Cardiovascular Diagnostics
• Medical Device Evaluation
• Point-of-Care Testing

Background:

• Activated clotting time (ACT) is a critical point-of-care test for managing heparinization during cardiac catheterization.
• Lack of standardization leads to significant variability in ACT results across different instruments.
• Understanding device-specific performance is crucial for accurate clinical decision-making.

Purpose of the Study:

• To compare the reproducibility and variability of ACT measurements between the HemoTec ACT and Hemochron 801 instruments.
• To assess the comparability of ACT results from these two devices, particularly within therapeutic ranges.
• To evaluate the overall performance and reliability of each ACT device.

Main Methods:

• Duplicate paired ACT tests were performed on 359 patients using both HemoTec and Hemochron devices (n=885).
• Prothrombin times (PT) and activated partial thromboplastin times (aPTT) were measured on subsets of samples.
• Statistical analyses were employed to determine performance, reproducibility, and relationships between the devices.

Main Results:

• While the average difference between devices was 8 seconds, over 60% of measurements varied by more than 10%, and over 25% varied by more than 20%.
• The HemoTec instrument exhibited superior reproducibility (mean CV 2.4% ± 3.1%) compared to the Hemochron (7.2% ± 6.1%; P < 0.00001).
• ACT results from HemoTec and Hemochron were nonlinear and not comparable within the therapeutic range of 200-350 seconds.

Conclusions:

• Significant variability exists in ACT measurements between HemoTec and Hemochron devices.
• The HemoTec ACT demonstrates better overall performance and reproducibility than the Hemochron 801.
• Clinical decisions based on ACT values should consider the specific instrument used due to non-comparable results.