Activated partial thromboplastin time derivative curves: helpful diagnostic tool in mixing test interpretation

Eren S. E., Karakukcu Ç., Ciraci M. Z., Ustundag Y., KARAKÜKCÜ M.

BLOOD COAGULATION & FIBRINOLYSIS, vol.29, no.4, pp.410-414, 2018 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 29 Issue: 4
  • Publication Date: 2018
  • Doi Number: 10.1097/mbc.0000000000000728
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.410-414
  • Keywords: blood coagulation tests, lupus coagulation inhibitor, mixing test, TOP COAGULATION ANALYZER, LUPUS ANTICOAGULANTS, DEFICIENCIES, ERRORS
  • Erciyes University Affiliated: Yes


The mixing test is used to evaluate whether prolonged activated partial thromboplastin time (APTT) is due to an inhibitor or a factor deficiency. The coagulation reaction is demonstrated with APTT derivative curves on the ACL TOP series. We aimed to determine the utility of APTT derivative curves in the mixing test process. The plasma of a patient was mixed with normal plasma in a 1:1 ratio and APTT assay was performed with SynthASil reagent. We observed roughness, biphasic and shoulder patterns in derivative curves during the mixing test. An extended laboratory investigation revealed a positive lupus anticoagulant, low factors XI and IX activities. Along with mixing test cut-off limits, we recommend analysing changes in APTT derivative curves to minimize erroneous interpretations of the mixing test. Derivative curves display either a normalizing pattern in factor deficiencies or an atypical pattern in the presence of lupus anticoagulant.