Sex Transm Dis. 2018 May;45(5):332-336. doi: 10.1097/OLQ.0000000000000756.
Trichomonas vaginalis is a sexually transmitted infection associated with increased transmission of HIV and significant adverse birth outcomes; culture and polymerase chain reaction (PCR) are commonly used in diagnosis.
Consenting HIV-infected pregnant women were recruited from clinics in South Africa and screened for T. vaginalis using PCR. Polymerase chain reaction-positive women provided an additional sample for culture. We compared T. vaginalis detection between PCR and culture, and investigated how PCR cycle threshold (Ct) values differ among culture results.
A total of 359 women were enrolled and 76 (20%) tested T. vaginalis PCR positive. Cultures were obtained from 61 of the PCR-positive women, and 38 (62%) were culture positive. The median baseline Ct of the PCR-positive/culture-positive group was 22.6 versus 38.0 among those who were PCR positive/culture negative (P < 0.001). Culture-positive cases had lower Ct values (higher DNA load); a Ct value less than 30 predicted positivity with a sensitivity of 97% and a specificity of 96%.
Culture was positive in roughly half of PCR-positive cases. The culture-negative cases had significantly higher Ct values, indicating a lower concentration of T. vaginalis DNA. A Ct value of 30 provides a reliable threshold for predicting culture positivity. The clinical significance of culture-negative infections detected by PCR is still unclear.
阴道毛滴虫是一种性传播感染，与 HIV 传播增加和不良出生结局显著相关；培养和聚合酶链反应（PCR）常用于诊断。
从南非的诊所招募同意参加的 HIV 感染孕妇，并使用 PCR 筛查阴道毛滴虫。PCR 阳性的女性提供额外的样本进行培养。我们比较了 PCR 和培养之间的阴道毛滴虫检测，并研究了培养结果之间的 PCR 循环阈值（Ct）值有何不同。
共纳入 359 名女性，76 名（20%）检测到阴道毛滴虫 PCR 阳性。从 61 名 PCR 阳性的女性中获得了培养物，其中 38 名（62%）培养阳性。PCR 阳性/培养阳性组的中位基线 Ct 值为 22.6，而 PCR 阳性/培养阴性组为 38.0（P<0.001）。培养阳性病例的 Ct 值较低（DNA 载量较高）；Ct 值小于 30 预测阳性的敏感性为 97%，特异性为 96%。
约一半的 PCR 阳性病例培养阳性。培养阴性病例的 Ct 值显著较高，表明阴道毛滴虫 DNA 浓度较低。Ct 值为 30 可提供预测培养阳性的可靠阈值。PCR 检测到的培养阴性感染的临床意义仍不清楚。
