Unexpected, isolated activated partial thromboplastin time prolongation: A practical mini‐review

• Published in: European journal of haematology Vol. 104; no. 6; pp. 519 - 525
• Main Authors: Rasmussen, Katrine Laura, Philips, Malou, Tripodi, Armando, Goetze, Jens Peter
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.06.2020
• Subjects: activated partial thromboplastin time; Algorithms; Anticoagulants; Blood Coagulation; Blood Coagulation Disorders - diagnosis; Blood Coagulation Disorders - epidemiology; Blood Coagulation Disorders - etiology; Blood Coagulation Factors; Clinical Decision-Making; Coagulation factors; Diagnosis, Differential; Disease Management; Disease Susceptibility; Drug Interactions; Hemophilia; Heparin; Humans; Incidental Findings; International Normalized Ratio; Laboratories; lupus anticoagulants; Lupus Coagulation Inhibitor; Partial Thromboplastin Time - methods; Partial Thromboplastin Time - standards; Patients; Prevalence; Prothrombin; Surgery; Thromboplastin; lupus anticoagulants; hemophilia; activated partial thromboplastin time
• ISSN: 0902-4441; 1600-0609
• DOI: 10.1111/ejh.13394

A common inquiry in coagulation laboratories is how to interpret an unexpected, isolated prolonged activated partial thromboplastin time (APTT). In this context, isolated means together with a normal prothrombin time (PT) and/or normal international normalized ratio (INR). This finding may lead to contact with laboratory doctors for further advice on a diagnostic strategy. Occasionally, the need for a diagnostic algorithm can be subacute, where surgery has to be postponed until an explanation for the isolated, prolonged APTT has been established. Activated partial thromboplastin time as a coagulation test was developed to monitor patients with hemophilia. Different APTT reagents display considerable differences in their sensitivity to deficiencies of coagulation factors. An isolated, prolonged APTT is seen in (a) individuals/patients with lupus anticoagulants, (b) patients in treatment with anticoagulants, mainly heparin, and (c) patients with deficiencies of specific coagulation factors. In this tutorial review, we summarize what may cause an isolated prolonged APTT and we present a simple diagnostic algorithm to differentiate between lupus anticoagulants (common) and factor deficiencies (rare). The identification of an isolated prolonged APTT as well as the underlying cause can be of the utmost importance in ensuring the correct therapeutic follow‐up.