A "percent correction" formula for evaluation of mixing studies

Area of Science:

• Clinical Chemistry
• Hematology
• Diagnostic Laboratory Medicine

Background:

• Mixing studies are crucial for diagnosing coagulation disorders.
• Evaluating prolonged activated partial thromboplastin time (aPTT) and/or prothrombin time (PT) requires accurate interpretation of mixing studies.
• Existing methods for evaluating mixing studies may have limitations in sensitivity and specificity.

Purpose of the Study:

• To evaluate the efficacy of a "percent correction" formula for interpreting mixing study results.
• To compare the diagnostic performance of a 4:1 plasma mix versus a 1:1 plasma mix.
• To assess the impact of incubation on the accuracy of the 4:1 mix testing.

Main Methods:

• The study analyzed patient plasma mixed with citrated normal plasma at ratios of 1:1 and 4:1.
• A "percent correction" formula was applied to assess mixing study results.
• Three different definitions of correction were evaluated.
• Activated partial thromboplastin time (aPTT) and prothrombin time (PT) were measured, with and without incubation.

Main Results:

• The percent correction formula using a 4:1 mix demonstrated good sensitivity and specificity for detecting anticoagulants and factor deficiencies, outperforming the 1:1 mix.
• The three evaluated definitions of correction showed poor sensitivity in detecting anticoagulants.
• The 4:1 aPTT mix testing with incubation exhibited improved sensitivity and specificity compared to immediate testing.

Conclusions:

• The percent correction formula with a 4:1 plasma mix provides a simple, objective, and effective criterion for evaluating mixing studies.
• This method enhances the detection of coagulation abnormalities compared to the 1:1 mix.
• The 4:1 mix, particularly with incubation, offers a valuable tool in coagulation diagnostics.