The Royal London Haemophilia Centre, Barts Health NHS Trust, London, UK.
NHS East and South East London Pathology Partnership, Barts Health NHS Trust, London, UK.
J Thromb Haemost. 2021 Aug;19(8):2007-2013. doi: 10.1111/jth.15362. Epub 2021 Jul 5.
Vaccine-induced immune thrombocytopenia and thrombosis (VITT) following ChAdOx1 nCOV-19 vaccine has been described, associated with unusual site thrombosis, thrombocytopenia, raised D-dimer, and high-titer immunoglobulin-G (IgG) class anti-platelet factor 4 (PF4) antibodies. Enzyme-linked immunosorbent assays (ELISA) have been shown to detect anti-PF4 in patients with VITT, but chemiluminescence assays do not reliably detect them. ELISA assays are not widely available in diagnostic laboratories, and, globally, very few laboratories perform platelet activation assays.
Assays that are commercially available in the United Kingdom were evaluated for their ability to identify anti-PF4 antibodies in samples from patients with suspected VITT. Four IgG-specific ELISAs, two polyspecific ELISAs, and four rapid assays were performed on samples from 43 patients with suspected VITT from across the United Kingdom. Cases were identified after referral to the UK Expert Haematology Panel multidisciplinary team and categorized into unlikely, possible, or probable VITT.
We demonstrated that the HemosIL AcuStar HIT-IgG, HemosIL HIT-Ab, Diamed PaGIA gel, and STic Expert assays have poor sensitivity for VITT in comparison to ELISA. Where these assays are used for heparin-induced thrombocytopenia (HIT) diagnosis, laboratories should ensure that requests for suspected VITT are clearly identified so that an ELISA is performed. No superiority of IgG-ELISAs over polyspecific ELISAs in sensitivity to VITT could be demonstrated. No single ELISA method detected all possible/probable VITT cases; if a single ELISA test is negative, a second ELISA or a platelet activation assay should be considered where there is strong clinical suspicion.
在接种 ChAdOx1 nCOV-19 疫苗后出现的疫苗诱导免疫性血小板减少症和血栓形成（VITT）与不常见的血栓部位、血小板减少症、D-二聚体升高和高滴度免疫球蛋白 G（IgG）类抗血小板因子 4（PF4）抗体有关。酶联免疫吸附试验（ELISA）已被证明可检测 VITT 患者中的抗-PF4，但化学发光测定法不能可靠地检测到它们。ELISA 测定法在诊断实验室中并不广泛使用，并且在全球范围内，很少有实验室进行血小板活化测定。
评估了在英国可商购的测定法，以确定它们识别疑似 VITT 患者样本中抗-PF4 抗体的能力。对来自英国各地的 43 名疑似 VITT 患者的样本进行了四项 IgG 特异性 ELISA、两项多特异性 ELISA 和四项快速测定。在向英国专家血液学小组多学科团队转诊后确定了病例，并将其分为不太可能、可能或很可能的 VITT。
我们证明，与 ELISA 相比，HemosIL AcuStar HIT-IgG、HemosIL HIT-Ab、Diamed PaGIA 凝胶和 STic Expert 测定法在 VITT 中的敏感性较差。在这些测定法用于肝素诱导的血小板减少症（HIT）诊断的情况下，实验室应确保明确识别出疑似 VITT 的请求，以便进行 ELISA。在敏感性方面，IgG-ELISA 并没有优于多特异性 ELISA。没有任何一种 ELISA 方法能检测到所有可能/很可能的 VITT 病例；如果单个 ELISA 测试为阴性，在强烈的临床怀疑下，应考虑进行第二种 ELISA 或血小板活化测定。
