Evaluation of prothrombin time and activated partial thromboplastin time mixing studies using an estimated factor...

Area of Science:

• Hematology
• Clinical Chemistry
• Diagnostic Medicine

Background:

• Prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT) mixing studies are crucial for diagnosing coagulation disorders.
• Distinguishing between factor deficiencies and inhibitors is essential for appropriate patient management.
• Current interpretation methods may lack accuracy, especially in cases with multiple deficiencies or inhibitors.

Purpose of the Study:

• To introduce and validate a novel method, Estimated Factor Correction (EFC), for interpreting PT/aPTT mixing studies.
• To compare the diagnostic performance of the EFC method against traditional approaches like normal range, percentage correction, and Rosner index.
• To assess the prevalence of isolated deficiencies, isolated inhibitors, and combined findings in patient samples.

Main Methods:

• Development of factor level versus PT/aPTT curves for various deficiency types (single, vitamin K-dependent, multiple).
• Utilizing these curves to predict factor levels and estimate necessary correction to differentiate inhibitors from deficiencies.
• Comparative analysis of the EFC method against established interpretation methods using known samples and patient data.

Main Results:

• The EFC method demonstrated superior accuracy in identifying known inhibitors (38/39) and differentiating deficiencies from inhibitors in patient samples (50/59).
• Analysis of 99 adult patient mixing studies revealed a significant proportion (40%) with evidence of both deficiency and inhibitor.
• The EFC method proved more accurate than comparison methods in determining the cause of prolonged PT/aPTT.

Conclusions:

• The Estimated Factor Correction (EFC) method offers a more accurate and reliable approach to interpreting PT/aPTT mixing studies.
• This novel method enhances the ability to differentiate between coagulation factor deficiencies and inhibitors, including complex cases.
• The findings support the clinical utility of the EFC method in routine coagulation diagnostics.