探討免疫作用引起血小板低下症之檢測方法

Review of Laboratory Tests for Immune-mediated Thrombocytopenia

黃瀅潔(Ying-Chieh Huang) ； 陳怡行(Yi-Hsing Chen) ； 張錦標(Jin-Biou Chang)

《中華職業醫學雜誌》 25卷2期 (2018/04) Pp. 115-124

摘要

臨床定義“血小板低下”為血液中的血小板低於150.000/ul。造成血小板低下的原因相當多，其中因免疫作用所引起的血小板低下是重要因素之一，主要是抗體攻擊血小板導致血液中的血小板破壞增加所致。相關的臨床疾病包括：特發性血小板低下、輸血後紫斑症、血小板輸注無效及新生兒異體免疫血小板低下症等。這些抗體對應的抗原主要為 Human platelet antigen (HPA)或Human leukocyte antigen (HLA)。與白血球之差異是血小板僅表現 HLA Class I，異體抗體免疫作用機制大多是Class I抗體所引起。臨床檢驗室常用血清學及分子生物學之分析方法，協助臨床醫師鑑別診斷免疫或非免疫病因所引起的血小板低下症。傳統的免疫酵素分析方法經改進後，提高分析的靈敏度及特異性，如MAIPA (monoclonal antibody-specific immobilization of platelet antigens)、PAC (platelet antigen capture immunoassays)。檢驗室應用分子生物學方法以鑑定基因型別，搭配抗體檢測協助臨床診斷，如新生兒異體血小板低下。本篇研究主要是探討免疫作用所引起的血小板低下症，綜整檢驗室檢測血小板抗原抗體之分析方法，並比較其優缺點，提供醫檢師及相關醫療人員選擇檢驗方法之參考。

關鍵字

血小板低下症 ； 血小板抗體 ； 血小板特異性抗原

並列摘要

Thrombocytopenia is defined by a platelet count lower than 150.000/ul in the blood. There are many conditions that may cause thrombocytopenia. One of the major cause is unwanted immune responses. Abnormal antibodies attack patient's platelets and lead to increasing destruction of the platelets. Immune-mediated thrombocytopenia include immune thrombocytopenia purpura(ITP), post-transfusion purpura (PTP), platelet transfusion refractoriness (PTR), neonatal alloimmune thrombocytopenia (NAIT), etc. The major antigens causing these antibodies are human platelet antigen (HPA) and human leukocyte antigen (HLA). Different from leukocytes, platelets express HLA Class I antigen only. Therefore, HLA Class I antibodies are the major antibodies mediate the alloimmune responses. Current clinical medical laboratories provide serological and molecular methods to differentiate whether thrombocytopenia is immune or non-immune mediated. There are several modified methods to improve the sensitivity and specificity of traditional enzyme-linked immunsorbent assay, such as monoclonal antibody-specific immobilization of platelet(MAIP) and platelet antigen capture immunoassays(PAC). Molecular methods combined with antibodies assay are helpful in diagnosing special clinical conditions like NAIT. This article reviewed the clinical manifestations of major immune-mediated thrombocytopenia and summarizes currently available relevant clinical laboratory tests.

並列關鍵字

thrombocytopenia ； anti-platelet antibodies ； human platelet antigen