Daka Bledar, Svensson Maria K, Lernmark Ke, Mincheva-Nilsson Lucia, Hallmans Goran, Rolandsson Olov
Department of Public Health and Clinical Medicine, Umeå University, Sweden.
Autoimmunity. 2009 Sep;42(6):507-14. doi: 10.1080/08916930902911720.
Autoantibodies against glutamic acid decarboxylase (GAD65Ab) are used in the classification of diabetes in adults. We assessed the concordance in GAD65 autoantibody levels within subjects between three different GAD65Ab radio binding assays (RBA). Plasma samples from 112 diabetes patients (median age 50 years) initially classified with type 2 diabetes was randomly selected from a local diabetes registry. Coded samples were analyzed with two RBA employing (35)S-labeled GAD65. The first used the pEx9 plasmid (pEx9 RBA), the second employed the pThGAD65 plasmid (pThGAD65 RBA) to label GAD65 by in vitro transcription translation. We also used a commercial kit employing plasmid pGAD17 labelled with (125)I (pGAD17 RBA). Subsequent analyses followed standard procedures. Two different cut-offs for GAD65Ab positivity were used in all three assays. We calculated the correlation, concordance, and agreement between the assays. The proportion of GAD65Ab positivity differed between assays when low cut-offs were used (pEx9 RBA 25%, pThGAD65 RBA 17.9%, and pGAD17 RBA 12.5%, respectively). When high cut-offs were applied, the concordance between the pEx9 RBA and the pThGAD65 RBA was 97.3 while their concordance to the pGAD17 RBA was lower (88.4 and 87.4, respectively). There was a low agreement between both pEx9 RBA and pGAD17 RBA (0.45, 95% CI 0.20-0.70) and between pThGAD65 RBA and pGAD17 RBA (0.43, 95% CI 0.18-0.68). We found discrepancies in determining the GAD65Ab positivity, which constitutes a problem when GAD65Ab are used clinically. Further methodological GAD65Ab assays studies are warranted.
抗谷氨酸脱羧酶（GAD65）自身抗体用于成人糖尿病的分类。我们评估了三种不同的GAD65自身抗体放射结合分析（RBA）方法在受试者体内GAD65自身抗体水平的一致性。从当地糖尿病登记处随机选取112例最初分类为2型糖尿病的糖尿病患者（中位年龄50岁）的血浆样本。用两种采用（35）S标记GAD65的RBA分析编码样本。第一种使用pEx9质粒（pEx9 RBA），第二种采用pThGAD65质粒（pThGAD65 RBA）通过体外转录翻译标记GAD65。我们还使用了一种采用用（125）I标记的pGAD17质粒的商业试剂盒（pGAD17 RBA）。后续分析遵循标准程序。所有三种分析均使用两种不同的GAD65自身抗体阳性临界值。我们计算了各分析方法之间的相关性、一致性和一致性。当使用低临界值时，各分析方法中GAD65自身抗体阳性的比例不同（pEx9 RBA为25%，pThGAD65 RBA为17.9%，pGAD17 RBA为12.5%）。当应用高临界值时，pEx9 RBA与pThGAD65 RBA之间的一致性为97.3，而它们与pGAD17 RBA的一致性较低（分别为88.4和87.4）。pEx9 RBA与pGAD17 RBA之间以及pThGAD65 RBA与pGAD17 RBA之间的一致性较低（分别为0.45，95%CI 0.20 - 0.70和0.43，95%CI 0.18 - 0.68）。我们发现在确定GAD65自身抗体阳性方面存在差异，这在临床使用GAD65自身抗体时构成一个问题。有必要进一步开展GAD65自身抗体分析方法的研究。
