QIMR Berghofer Medical Research Institute, Brisbane, Australia.
Menzies School of Health Research, Charles Darwin University, Darwin, Australia.
PLoS Negl Trop Dis. 2021 Feb 24;15(2):e0009149. doi: 10.1371/journal.pntd.0009149. eCollection 2021 Feb.
BACKGROUND: The suboptimal sensitivity and specificity of available diagnostic methods for scabies hampers clinical management, trials of new therapies and epidemiologic studies. Additionally, parasitologic diagnosis by microscopic examination of skin scrapings requires sample collection with a sharp scalpel blade, causing discomfort to patients and difficulty in children. Polymerase chain reaction (PCR)-based diagnostic assays, combined with non-invasive sampling methods, represent an attractive approach. In this study, we aimed to develop a real-time probe-based PCR test for scabies, test a non-invasive sampling method and evaluate its diagnostic performance in two clinical settings. METHODOLOGY/PRINCIPAL FINDINGS: High copy-number repetitive DNA elements were identified in draft Sarcoptes scabiei genome sequences and used as assay targets for diagnostic PCR. Two suitable repetitive DNA sequences, a 375 base pair microsatellite (SSR5) and a 606 base pair long tandem repeat (SSR6), were identified. Diagnostic sensitivity and specificity were tested using relevant positive and negative control materials and compared to a published assay targeting the mitochondrial cox1 gene. Both assays were positive at a 1:100 dilution of DNA from a single mite; no amplification was observed in DNA from samples from 19 patients with other skin conditions nor from house dust, sheep or dog mites, head and body lice or from six common skin bacterial and fungal species. Moderate sensitivity of the assays was achieved in a pilot study, detecting 5/7 (71.4% [95% CI: 29.0% - 96.3%]) of clinically diagnosed untreated scabies patients). Greater sensitivity was observed in samples collected by FLOQ swabs compared to skin scrapings. CONCLUSIONS/SIGNIFICANCE: This newly developed qPCR assay, combined with the use of an alternative non-invasive swab sampling technique offers the possibility of enhanced diagnosis of scabies. Further studies will be required to better define the diagnostic performance of these tests.
背景:现有的疥疮诊断方法的敏感性和特异性不理想,这给临床管理、新疗法的试验和流行病学研究带来了困难。此外,通过皮肤刮片的显微镜检查进行寄生虫诊断需要使用锋利的手术刀刀片进行样本采集,这会给患者带来不适,也给儿童带来困难。基于聚合酶链反应(PCR)的诊断检测方法与非侵入性采样方法相结合,是一种很有吸引力的方法。在这项研究中,我们旨在开发一种用于疥疮的实时探针 PCR 检测方法,测试一种非侵入性采样方法,并在两种临床环境中评估其诊断性能。
方法/主要发现:在疥疮的草案基因组序列中确定了高拷贝数重复 DNA 元件,并将其用作诊断 PCR 的检测靶标。鉴定出两个合适的重复 DNA 序列,一个 375 碱基对的微卫星(SSR5)和一个 606 碱基对的串联重复(SSR6)。使用相关的阳性和阴性对照材料测试了诊断敏感性和特异性,并与靶向线粒体 cox1 基因的已发表检测方法进行了比较。两个检测方法在 1:100 稀释的单个螨虫 DNA 时均为阳性;在来自 19 名患有其他皮肤疾病的患者的样本中,在来自房屋灰尘、绵羊或狗螨虫、头虱和体虱以及六种常见皮肤细菌和真菌物种的样本中均未观察到扩增。在一项试点研究中,该检测方法的敏感性适中,检测到 7 例(71.4%[95%CI:29.0% - 96.3%])未经治疗的临床诊断为疥疮的患者中的 5 例。与皮肤刮片相比,FLOQ 拭子采集的样本检测到更高的敏感性。
结论/意义:这种新开发的 qPCR 检测方法与替代的非侵入性拭子采样技术相结合,为增强疥疮的诊断提供了可能。需要进一步的研究来更好地定义这些检测方法的诊断性能。
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