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. 2018 Jul;32(6):e22415.
doi: 10.1002/jcla.22415. Epub 2018 Feb 27.

What should be the laboratory approach against isolated prolongation of a activated partial thromboplastin time?

Mesude Falay  1 , Mehmet Senes  2 , Dogan Yücel  2 , Turan Turhan  3 , Simten Dagdaş  1 , Melike Pekin  1 , Namik K Nazaroglu  4 , Gülsüm Özet  1
Affiliations

What should be the laboratory approach against isolated prolongation of a activated partial thromboplastin time?

Mesude Falay et al. J Clin Lab Anal. 2018 Jul.

Abstract

Background: This study is a retrospective evaluation of patients who were subject to mixing study in our laboratory due to prolonged APTT. The preliminary diagnoses, clinical manifestations, and results of additional ordered tests were reviewed. The study aims to investigate whether repeating APTT test with a different assay prior to performing mixed study in patients with prolonged APTT would be a better alternative algorithmic approach in order to save both time and costs.

Methods: We retrospectively evaluated 166 patients (65 females and 101 males) who were subject to mixing study due to isolated prolonged APTT. Additional ordered tests to identify the etiology and clinical findings were reviewed. All patients who had prolonged APTT as a result of testing with Hemosil Synthasil APTT reagent in ACL TOP analyzer were repeated with Stago Cephascreen APTT reagent in STA-R coagulation analyzer.

Results: APTT test was requested preoperatively in 72.2% of cases. Only 6.6% of the cases had history of bleeding. Correction with mixing study was achieved in 122 (73.5%) cases, among which 75 (45%) cases were found to have APTT test results within reference range when tested with Cephascreen reagent. In 44 (26.5%) cases, mixing study did not result in correction. Only 4 cases were confirmed to have lupus anticoagulants (LA), while 4 cases were diagnosed with hemophilia with inhibitors.

Conclusion: Prolonged APTT results should always be retested using a different assay prior to mixing study. The clinician and the laboratory specialist should collaborate at the postanalytical phase.

Keywords: APTT; coagulation; mixing test.

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Figures

Figure 1
Figure 1
Cases with corrected results in mixing study
Figure 2
Figure 2
Cases with n no correction in mixing study and Cephascreen APTT prolonged. *2 cases use DOAC. **2 cases use DOAC
Figure 3
Figure 3
APTT test results showed significant difference between ACL Top, Stago STA‐R, and mixing study groups (P < .0001)
Figure 4
Figure 4
ACL TOP and Stago STA‐R regression analysis correlation graphic ACL Top = 1.109 Stago STA‐R + 2.48 (r = .943, P < .001)
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