Centre Hospitalier Régional Universitaire (CHRU) of Montpellier and University Montpellier I (Faculty of Medicine), Department of Parasitology-Mycology and Molecular Biology Pole of the French National Reference Centre for Toxoplasmosis, Montpellier, France.
J Clin Microbiol. 2012 Dec;50(12):3944-51. doi: 10.1128/JCM.00918-12. Epub 2012 Oct 3.
From a prospective cohort of 344 women who seroconverted for toxoplasmosis during pregnancy, 344 amniotic fluid, 264 placenta, and 216 cord blood samples were tested for diagnosis of congenital toxoplasmosis using the same PCR assay. The sensitivity and negative predictive value of the PCR assay using amniotic fluid were 86.3% and 97.2%, respectively, and both specificity and positive predictive value were 100%. Using placenta and cord blood, sensitivities were 79.5% and 21.2%, and specificities were 92% and 100%, respectively. In addition, the calculation of pretest and posttest probabilities and the use of logistic regression allowed us to obtain curves that give a dynamic interpretation of the risk of congenital toxoplasmosis according to gestational age at maternal infection, as represented by the three sample types (amniotic fluid, placenta, and cord blood). Two examples are cited here: for a maternal infection at 25 weeks of amenorrhea, a negative result of prenatal diagnosis allowed estimation of the probability of congenital toxoplasmosis at 5% instead of an a priori (pretest) risk estimate of 33%. For an infection at 10 weeks of amenorrhea associated with a pretest congenital toxoplasmosis risk of 7%, a positive PCR result using placenta at birth yields a risk increase to 43%, while a negative result damps down the risk to 0.02%. Thus, with a molecular diagnosis performing at a high level, and in spite of the persistence of false negatives, posttest risk curves using both negative and positive results prove highly informative, allowing a better assessment of the actual risk of congenital toxoplasmosis and finally an improved decision guide to treatment.
从 344 名在怀孕期间血清学转化为弓形虫感染的前瞻性队列中，对 344 份羊水、264 份胎盘和 216 份脐带血样本使用相同的 PCR 检测方法进行了先天性弓形虫病的诊断检测。PCR 检测羊水的灵敏度和阴性预测值分别为 86.3%和 97.2%，特异性和阳性预测值均为 100%。使用胎盘和脐带血，灵敏度分别为 79.5%和 21.2%，特异性分别为 92%和 100%。此外，通过计算预测试验和后测试概率以及使用逻辑回归，我们可以获得曲线，根据母体感染的妊娠周数（以三种样本类型[羊水、胎盘和脐带血]表示），对先天性弓形虫病的风险进行动态解释。这里引用了两个例子：对于母体感染的妊娠 25 周，产前诊断的阴性结果可以估计先天性弓形虫病的概率为 5%，而不是先验（预测试验）风险估计值的 33%。对于感染妊娠 10 周且预测试验先天性弓形虫病风险为 7%的患者，出生时胎盘的 PCR 阳性结果会使风险增加到 43%，而阴性结果则会将风险降低至 0.02%。因此，在分子诊断水平较高的情况下，尽管存在假阴性，使用阴性和阳性结果的后测试风险曲线仍然具有高度的信息性，能够更好地评估先天性弓形虫病的实际风险，并最终为治疗提供更好的决策指南。
