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.