The accurate determination of ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type 1 motif, member 13) activity is imperative for effective diagnosis and treatment strategies in thrombotic microangiopathies (TMA). Amongst its benefits, this feature allows for the identification and subsequent distinction between thrombotic thrombocytopenic purpura (TTP) and other thrombotic microangiopathies (TMAs), thus prompting an appropriately tailored therapeutic approach. Commercially available, both manual and automated, are quantitative ADAMTS13 activity assays, some yielding results in less than an hour; nevertheless, their practical application is hampered by the indispensable need for specialized equipment and personnel, found primarily in specialized diagnostic facilities. find more Employing flow-through technology and an ELISA activity assay principle, the Technoscreen ADAMTS13 Activity test is a commercially available, rapid, semi-quantitative screening test. This screening tool is simple to use, and it does not require specialized equipment or personnel. Four intensity levels on a color chart, corresponding to ADAMTS13 activity (0, 0.1, 0.4, and 0.8 IU/mL), are used as a benchmark for the colored end point. A quantitative assay is crucial to confirm the reduced levels detected in the screening test. The assay's design facilitates its implementation in nonspecialized labs, distant sites, and immediate-care settings.

A consequence of low levels of ADAMTS13, a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13, is the prothrombotic disorder, thrombotic thrombocytopenic purpura (TTP). Through its action, ADAMTS13, also called von Willebrand factor (VWF) cleaving protease (VWFCP), breaks down VWF multimers, hence lowering the plasma activity of VWF. Without ADAMTS13, typically observed in thrombotic thrombocytopenic purpura (TTP), plasma von Willebrand factor (VWF) builds up, specifically as extremely large multimeric forms, ultimately causing a thrombotic event. In confirmed instances of thrombotic thrombocytopenic purpura (TTP), acquired ADAMTS13 deficiency is frequently observed. This is a consequence of antibodies generated against ADAMTS13, which can either lead to its clearance from the circulatory system or impede its enzymatic activity. Oral antibiotics This report describes an assessment protocol for ADAMTS13 inhibitors, antibodies that interfere with the function of ADAMTS13. To identify inhibitors to ADAMTS13, the protocol employs a Bethesda-like assay, which tests mixtures of patient and normal plasma to measure residual ADAMTS13 activity, reflecting the technical steps involved. Assessment of residual ADAMTS13 activity is possible through diverse assays, including a rapid 35-minute test on the AcuStar instrument (Werfen/Instrumentation Laboratory), as illustrated in this protocol.

A significant deficiency of the ADAMTS13 enzyme, a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13, causes the prothrombotic condition known as thrombotic thrombocytopenic purpura (TTP). A shortage of ADAMTS13, typical of thrombotic thrombocytopenic purpura (TTP), allows an accumulation of large von Willebrand factor (VWF) multimers in the bloodstream. Consequently, this abnormal buildup contributes to pathological platelet clumping and the formation of blood clots. In a spectrum of conditions, including secondary thrombotic microangiopathies (TMA) – such as those induced by infections (e.g., hemolytic uremic syndrome (HUS)), liver disease, disseminated intravascular coagulation (DIC), and sepsis – ADAMTS13, in addition to its presence in TTP, may be mildly to moderately decreased. This can also occur during acute/chronic inflammatory conditions and sometimes during COVID-19 (coronavirus disease 2019). ADAMTS13 can be identified using a variety of methods, specifically ELISA (enzyme-linked immunosorbent assay), FRET (fluorescence resonance energy transfer), and chemiluminescence immunoassay (CLIA). According to CLIA standards, this report describes a protocol for determining the level of ADAMTS13. A rapid test, completed within 35 minutes, is specified by this protocol, usable on the AcuStar instrument (Werfen/Instrumentation Laboratory). Testing on a BioFlash instrument from the same company, however, may be permitted in specific regions.

Often termed von Willebrand factor cleaving protease (VWFCP), ADAMTS13 is a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13. ADAMTS13's effect is to divide VWF multimers, thereby decreasing the activity of VWF in the blood plasma. Thrombotic thrombocytopenic purpura (TTP) arises from a lack of ADAMTS13, causing a buildup of plasma von Willebrand factor (VWF), predominantly as large VWF multimers, ultimately resulting in thrombosis. A variety of conditions, encompassing secondary thrombotic microangiopathies (TMA), can also exhibit relative ADAMTS13 deficiencies. Within the current context of COVID-19 (coronavirus disease 2019), there appears to be a relationship between a relative reduction of ADAMTS13 and the pathological accumulation of VWF, which conceivably plays a significant role in the observed thrombotic tendency in affected patients. A range of assays can be employed to perform laboratory ADAMTS13 testing, supporting both the diagnosis and management of conditions such as TTP and TMA. This chapter, accordingly, presents a general overview of laboratory testing procedures for ADAMTS13 and the practical value of such testing in supporting the diagnosis and management of connected disorders.

For the diagnosis of heparin-induced thrombotic thrombocytopenia (HIT), the serotonin release assay (SRA) stands as the gold-standard assay for detecting heparin-dependent platelet-activating antibodies. A report surfaced in 2021 detailing a post-adenoviral vector COVID-19 vaccination instance of thrombotic thrombocytopenic syndrome. A severe immune platelet activation syndrome, vaccine-induced thrombotic thrombocytopenic syndrome (VITT), was clinically presented by unusual thrombotic events, low platelet counts, vastly elevated plasma D-dimer levels, and a high mortality rate, even when treated with intensive therapies including anticoagulation and plasma exchange. In both heparin-induced thrombocytopenia (HIT) and vaccine-induced thrombotic thrombocytopenia (VITT), the antibodies target platelet factor 4 (PF4), but critical differences are present in their mechanisms and effects. The SRA's improved detection of functional VITT antibodies stemmed from the required modifications. Platelet activation assays, a vital diagnostic tool, continue to be crucial in the evaluation of heparin-induced thrombocytopenia (HIT) and vaccine-induced immune thrombocytopenia (VITT). We illustrate the practical application of SRA to evaluate antibodies related to HIT and VITT.

The iatrogenic complication, heparin-induced thrombocytopenia (HIT), is a well-characterized problem that frequently arises from heparin anticoagulation, resulting in significant morbidity. A distinct adverse effect of adenoviral vaccines, such as ChAdOx1 nCoV-19 (Vaxzevria, AstraZeneca) and Ad26.COV2.S (Janssen, Johnson & Johnson) against COVID-19, is vaccine-induced immune thrombotic thrombocytopenia (VITT), a newly recognized severe prothrombotic complication. Laboratory testing for antiplatelet antibodies, using immunoassays and subsequently confirmed by functional assays for platelet-activating antibodies, is essential for the diagnosis of both HIT and VITT. Pathological antibody detection relies heavily on functional assays, as immunoassays exhibit inconsistent sensitivity and specificity. In response to plasma from patients suspected of having HIT or VITT, this chapter describes a novel whole blood flow cytometry assay for the detection of procoagulant platelets within healthy donor blood. Furthermore, a method for identifying suitable healthy donors for HIT and VITT testing is given.

Adverse reactions associated with the adenoviral vector COVID-19 vaccines, including AstraZeneca's ChAdOx1 nCoV-19 (AZD1222) and Johnson & Johnson's Ad26.COV2.S vaccine, led to the recognition of vaccine-induced immune thrombotic thrombocytopenia (VITT) in 2021. Characterized by severe immune platelet activation, VITT presents with an incidence of 1 to 2 cases for every 100,000 vaccinations. Symptoms of VITT, including thrombocytopenia and thrombosis, frequently appear within a 4 to 42 day period from the time of the first vaccine dose. Affected individuals produce platelet-activating antibodies that specifically recognize and bind to platelet factor 4 (PF4). An antigen-binding assay (enzyme-linked immunosorbent assay, ELISA) and a functional platelet activation assay are both recommended by the International Society on Thrombosis and Haemostasis for the diagnostic evaluation of VITT. A functional assay for VITT, using the technique of multiple electrode aggregometry (Multiplate), is described.

Heparin-dependent IgG antibodies, a key component in immune-mediated heparin-induced thrombocytopenia (HIT), bind to heparin/platelet factor 4 (H/PF4) complexes, leading to platelet activation. A substantial collection of assays exists for investigating heparin-induced thrombocytopenia (HIT), which fall under two distinct groups. Initially, antigen-based immunoassays detect all antibodies against H/PF4, acting as a preliminary diagnostic step. Finally, functional assays are required, specifically identifying those antibodies capable of activating platelets, thereby confirming a diagnosis of pathological HIT. While the serotonin-release assay (SRA) has served as the gold standard for decades, easier alternatives have become increasingly common over the past ten years. This chapter will delve into whole blood multiple electrode aggregometry, a validated method for functionally diagnosing heparin-induced thrombocytopenia.
Heparin-induced thrombocytopenia (HIT) occurs when the immune system produces antibodies against a complex formed by heparin and platelet factor 4 (PF4) subsequent to the introduction of heparin. Eus-guided biopsy Different immunological assays, encompassing enzyme-linked immunosorbent assay (ELISA) and chemiluminescence on the AcuStar instrument, are utilized for the identification of these antibodies.