Inhibitor Identification in the Coagulation Laboratory: Table 1

Abstract

Identifying an inhibitor of a coagulation factor is a challenging task. This process requires several steps and is not straightforward. In this article, I will attempt to simplify this complex process. The first step is to understand how specific and nonspecific antibodies affect coagulation. A specific antibody that is directed against a specific coagulation factor may result in bleeding. However, the risk of bleeding depends on which protein the coagulation inhibitor is directed against. For example, the most common severe acquired coagulation protein inhibitor is an antibody directed against Factor VIII. Patients with Factor VIII experience bleeding and prolonged activated partial thromboplastin time (aPTT). A nonspecific antibody may inhibit several factors and may not result in bleeding but in a thrombotic state. For example, lupus anticoagulant (LA) and antiphospholipid antibody are antibodies that are directed against epitopes of proteins bound to phospholipids. The persistence of LA in the presence with other antibodies, such as beta2-glycoprotein 1 (B2GPI), indicates a patient at thrombotic risk. Therefore, being able to distinguish between the different types of antibodies will help determine the risk to the patient of bleeding or a thrombotic event. The type of commercial reagents plays a significant role in antibody assessment. How sensitive is the reagent in detecting specific factor levels? Is your reagent sensitive or insensitive to LA? Knowing the answers to those questions will help interpretation of the results. It is important to know how sensitive your reagent is in detecting factor levels. In other words, what levels of factor will prolong the prothrombin time (PT) and/or aPTT? Most reagents should have a prolonged screening test when the level of factor falls below 30% in activity. If reagents are insensitive to a specific factor at a certain low level, PT … [↵][1]* To whom correspondence should be addressed. E-mail: dcastellone28{at}gmail.com [1]: #xref-corresp-1-1