Clin Lab. 2022 Aug 1;68(8). doi: 10.7754/Clin.Lab.2021.211112.
Ig (Immunglobulin) M detection and low avidity index are markers of recent infection in differentiating acute and chronic stages of Toxoplasma gondii (T. gondii) infections. In this study, we aimed to evaluate whether the anti-T. gondii IgM antibody index threshold value could be a predictive factor in the estimation of low avidity and its use in improving the diagnosis of early toxoplasma infection.
Anti-T. gondii IgM, IgG antibody and IgG avidity results were analyzed. Anti-T. gondii IgG and IgM antibodies in blood samples were studied with chemiluminescent microparticle immunoassay (CMIA), and IgG avidity test was performed with Enzyme Linked Fluorescent Assay (ELFA) technique.
The overall seroprevalence of anti-T. gondii antibodies (IgG and/or IgM) was 19.4%. Of the 64 patients whose avidity tests were studied, 47 (73.4%) were female. Twenty seven (57.4%) of the women were pregnant. In the IgG avidity test, 7.8% low avidity was detected. Low avidity was detected in only 4 (15.4%) of 26 IgM positive cases. IgM analysis of a case (6-month-old baby) with low avidity was found to be negative. In the prediction of low avidity, the assay's IgM positivity cutoff value was ≥ 0.6, its sensitivity, specificity, positive predictive value, and negative predictive value were 80%, 62.7%, 2.3%, and 99.7%, respectively. With Architect, 37.3% of samples were false positive. Determining the IgM index cutoff value was unsuccessful in distinguishing low avidity. The area under the ROC curve was 0.574 (p = 0.60).
In our study, the positive predictive value of the IgM test kit in estimating low avidity was low and the false positivity rate was 37.3%. It is thought that the index cutoff value of the anti-T. gondii IgM antibody test kit cannot be considered as a good predictor of recent infection. Studies with larger patient groups are needed.
免疫球蛋白 M（IgM）检测和低亲和力指数是区分刚地弓形虫（Toxoplasma gondii）急性和慢性感染阶段的近期感染标志物。在这项研究中，我们旨在评估抗弓形虫 IgM 抗体指数临界值是否可以作为低亲和力的预测因子，并用于提高早期弓形虫感染的诊断。
分析抗弓形虫 IgM、IgG 抗体和 IgG 亲和力结果。采用化学发光微粒子免疫分析（CMIA）检测血样中的抗弓形虫 IgG 和 IgM 抗体，采用酶联荧光分析（ELFA）技术进行 IgG 亲和力检测。
抗弓形虫抗体（IgG 和/或 IgM）的总体血清阳性率为 19.4%。在进行亲和力检测的 64 名患者中，47 名（73.4%）为女性。27 名（57.4%）女性为孕妇。在 IgG 亲和力检测中，检测到 7.8%的低亲和力。仅在 26 例 IgM 阳性病例中的 4 例（15.4%）中检测到低亲和力。对一例（6 个月大的婴儿）低亲和力的 IgM 分析结果为阴性。在低亲和力的预测中，该检测的 IgM 阳性截断值≥0.6，其灵敏度、特异性、阳性预测值和阴性预测值分别为 80%、62.7%、2.3%和 99.7%。采用 Architect，37.3%的样本为假阳性。确定 IgM 指数截断值无法区分低亲和力。ROC 曲线下面积为 0.574（p=0.60）。
在我们的研究中，IgM 检测试剂盒在估计低亲和力方面的阳性预测值较低，假阳性率为 37.3%。因此，抗弓形虫 IgM 抗体检测试剂盒的指数截断值不能被认为是近期感染的良好预测因子。需要进行更大患者群体的研究。
