Automated mixing studies and pattern recognition for the laboratory diagnosis of a prolonged activated partial thromboplastin time using an automated coagulation analyzer

Introduction: The objective of this study was to explore whether an automated coagulation analyzer could be applied to normal plasma mixing studies for the assessment of blood samples showing a prolonged activated partial thromboplastin time (APTT).

Materials and methods: Ten laboratory staff members performed normal plasma mixing studies and evaluated plasma samples using 3 different methods: (1) manual dilution and analysis, (2) manual dilution and automatic analysis with STA-R®, and (3) automatic dilution and analysis with the Coapresta® 2000 (CP2000). The time from the start of the analysis to the generation of the result plots and the plasma volumes required were determined. We analyzed patient plasma samples showing a prolonged APTT using the CP2000, and the result plots were categorized into 3 curve patterns based on the area ratio values: the inhibitor type (convex pattern), deficiency type (concave pattern), and suspicious inhibitor type (approximately straight pattern).

Results: When pooled patient plasma was used, the same patterns were obtained from normal plasma mixing studies using the 3 different methods. The time required to complete the mixing studies and the plasma volumes required were 28.2 ± 2.4 min and 350 μL for manual analysis, 23.2 ± 2.1 min and 875 μL for STA-R(®), and 8.5 +/- 0.1 min and 175 μL for CP2000, respectively. Of 31 patient samples, 9 were categorized into the inhibitor type, 15 were categorized into the deficiency type, and 7 were categorized into the suspicious inhibitor type.

Conclusions: The CP2000 analyzer is applicable to the laboratory diagnosis of a prolonged APTT using pattern recognition, as it requires a shorter time to complete mixing studies and a smaller plasma volume in comparison with manual analysis.