New Automated Immunoassay Measuring Immunoglobulin A Antigliadin Antibodies for Prediction of Celiac Disease in Childhood

The prevalence of celiac disease (CD) in Sweden is about 4 cases per 1,000 people. Screening for CD with serological tests indicates similar high prevalences in many other countries. Between 1 November 1992 and 30 April 1995, 133 children (9 months to 16.7 years of age) with suspected CD were studied. The predictive value (PV) of immunoglobulin A antigliadin antibodies (IgA-AGA) in the serum as assayed with two new commercial automated immunoassays—the Pharmacia CAP System Gliadin IgA FEIA (CAP) and the UNICAP-100 (UNICAP)—and with three “in-house” methods was evaluated using assessment of the small intestinal mucosa morphology as the “gold standard.” All serum samples were analyzed for total serum IgA. At presentation the diagnostic sensitivities and specificities of the different tests varied from 0.72 to 0.88 and 0.67 to 0.87, respectively. All methods showed a higher sensitivity for CD in younger children. The area under each assay's receiver operating characteristic curve was calculated and varied between 0.82 and 0.89. The positive and negative PVs for the CAP and UNICAP, which were assays with a high sensitivity and a high specificity, respectively, were estimated. In the clinically selected population (prevalence of CD, 1 in 3) the positive PV was about 55%, and in the general population (prevalence, 1 in 250) it was about 1%. The negative PVs for both CAP and UNICAP were close to 100%; thus, when the AGA test was negative, the risk for CD was small. Interestingly, five children had serum IgA levels below the detection limit (<0.07 g/liter) when on a gluten-free diet, whereas they had normal levels at the time of the first biopsy. In conclusion, the automated immunoassays—based on ImmunoCAP technology—for analysis of IgA-AGA had a reliability comparable to that of the in-house methods.

乳糜泻（celiac disease, CD）在瑞典的患病率约为每1000人中有4例。采用血清学检测筛查乳糜泻，在诸多其他国家中也显示出相近的高患病率。1992年11月1日至1995年4月30日期间，本研究纳入133名疑似乳糜泻的儿童（年龄范围9个月至16.7岁）开展分析。本研究以小肠黏膜形态学评估作为「金标准」，评估两种新型商业自动化免疫检测法——法玛西亚CAP系统麦胶蛋白IgA FEIA（CAP）与UNICAP-100（UNICAP），以及三种实验室自建方法（in-house）对血清免疫球蛋白A抗麦胶蛋白抗体（immunoglobulin A antigliadin antibodies, IgA-AGA）的预测价值（predictive value, PV）。所有血清样本均完成总血清IgA检测。入组阶段，不同检测方法的诊断灵敏度与特异度分别介于0.72至0.88、0.67至0.87之间。所有检测方法对低龄儿童的乳糜泻均展现出更高的诊断灵敏度。研究人员计算了各检测法的受试者工作特征曲线（receiver operating characteristic curve）下面积，其范围为0.82至0.89。针对分别具备高灵敏度与高特异度的CAP与UNICAP检测法，分别估算了其阳性与阴性预测价值。在临床筛选人群（乳糜泻患病率为1/3）中，阳性预测价值约为55%；而在普通人群（乳糜泻患病率为1/250）中，该数值约为1%。CAP与UNICAP的阴性预测价值均接近100%，因此当AGA检测结果为阴性时，罹患乳糜泻的风险极低。值得注意的是，有5名儿童在无麸质饮食（gluten-free diet）期间的血清IgA水平低于检测限（<0.07 g/L），但在首次活检时其血清IgA水平处于正常范围。综上，基于ImmunoCAP技术的自动化免疫检测法用于IgA-AGA分析，其可靠性与实验室自建方法相当。