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Evaluation of Activated Partial Thromboplastin Time Mixing Studies Using Several Methods.
Chaonan Liu1, Liqin Ling1, Xunbei Huang1
1From the Department of Laboratory Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan, China (Liu, Ling, Huang, Mi, Liao, Jia, Wang, Zhou).
Archives of Pathology & Laboratory Medicine
|March 10, 2022
Summary
Optimizing activated partial thromboplastin time (APTT) mixing studies improves diagnostic accuracy. Combining 1:1 and 4:1 mixing strategies enhances the ability to differentiate coagulation factor deficiencies and inhibitors.
Area of Science:
- Hematology
- Clinical Chemistry
- Diagnostic Medicine
Background:
- A prolonged activated partial thromboplastin time (APTT) is a critical indicator of coagulation disorders.
- Causes include factor deficiencies, factor inhibitors, and antiphospholipid antibodies.
- APTT mixing studies are essential for identifying the underlying cause of prolonged APTT.
Purpose of the Study:
- To optimize activated partial thromboplastin time (APTT) mixing studies.
- To evaluate and combine 1:1 and 4:1 mixing ratios for improved diagnostic accuracy.
Main Methods:
- Prospective enrollment of patients with prolonged APTT and normal prothrombin/thrombin times.
- Application of 1:1 mixing studies to all samples (n=251).
- Selective application of 4:1 mixing studies to a subset of samples (n=134).
Main Results:
- The study involved 251 samples: 116 with factor deficiencies, 75 with FVIII inhibitors, and 60 with antiphospholipid antibodies.
- A modified Rosner index and extended incubation time criteria demonstrated superior differentiation of deficiencies from inhibitors.
- Specific Rosner index ranges guided the optimal use of 1:1 versus 4:1 mixing studies for enhanced diagnostic accuracy.
Conclusions:
- APTT mixing studies exhibit good sensitivity and specificity.
- Combining 1:1 and 4:1 mixing studies significantly improves diagnostic capabilities over 1:1 alone.
- The proposed approach offers objective and effective criteria for interpreting APTT mixing study results.
