Alwar Vanamala, Devi A M Shanthala, Sitalakshmi S, Karuna R K
Department of Clinical Pathology, St John's Medical College Hospital, Sarjapur Road, Bangalore, 560034 India.
Indian J Hematol Blood Transfus. 2012 Mar;28(1):15-8. doi: 10.1007/s12288-011-0098-7. Epub 2011 Jul 21.
A positive direct Coombs test (DCT) is the hallmark of diagnosis of immune hemolytic anemias. The reagent used for the test is the Antihuman globulin (AHG), which may be either 'Polyspecific' or 'Monospecific'. The advent of the Gel card systems has made the procedure and interpretation of DCT simpler. Aim of this study is to evaluate three of the various techniques used for the performance and interpretation of DCT. A total of 96 EDTA samples were included in the study. DCT was performed by (i) polyspecific AHG manual tube method (ii) polyspecific AHG Gel card method and (iii) monospecific AHG (Anti IgG and Anti Complement) manual tube method. In our study we considered positivity by monospecific AHG as the standard for diagnosis. Of the total 96 samples evaluated, 44 cases positive by Gel card method, were also positive for either one or both the monospecific AHG reagents. 17 cases positive by Gel card were negative by all manual methods. These false positive cases were attributed to reasons such as increased ESR, macrocytosis and marked leucocytosis. Nine cases were negative by Gel card but were positive with the Monospecific AHG. The sensitivity of DCT done by the Gel card technique was 83.01% and the specificity was 60.46%. Use of Gel card technique to perform and interpret DCT is easier than manual tube methods, but positivity by Gel card needs to be correlated with clinical presentation of the patient and other laboratory findings. Monospecific antisera can be used to confirm cases that are positive by the Gel card systems.
直接抗人球蛋白试验（DCT）阳性是免疫性溶血性贫血诊断的标志。该试验所用试剂为抗人球蛋白（AHG），可分为“多特异性”或“单特异性”。凝胶卡系统的出现使DCT的操作和结果判读变得更简单。本研究的目的是评估用于DCT操作和结果判读的多种技术中的三种。共有96份乙二胺四乙酸（EDTA）样本纳入本研究。DCT采用以下方法进行：（i）多特异性AHG手工试管法；（ii）多特异性AHG凝胶卡法；（iii）单特异性AHG（抗IgG和抗补体）手工试管法。在我们的研究中，我们将单特异性AHG阳性作为诊断标准。在总共评估的96份样本中，凝胶卡法检测为阳性的44例样本，对一种或两种单特异性AHG试剂也呈阳性。凝胶卡法检测为阳性的17例样本，所有手工方法检测均为阴性。这些假阳性病例归因于红细胞沉降率（ESR）升高、大红细胞症和显著白细胞增多等原因。9例凝胶卡法检测为阴性，但单特异性AHG检测为阳性。凝胶卡技术进行DCT的敏感性为83.01%，特异性为60.46%。使用凝胶卡技术进行DCT的操作和结果判读比手工试管法更容易，但凝胶卡法检测为阳性的结果需要与患者的临床表现和其他实验室检查结果相关联。单特异性抗血清可用于确认凝胶卡系统检测为阳性的病例。
