Bahir Dar University, College of Medicine and Health Science, Bahir Dar, Ethiopia.
Barcelona Institute for Global Health (ISGlobal), Hospital Clínic-Universitat de Barcelona, Spain.
PLoS Negl Trop Dis. 2021 Feb 18;15(2):e0009076. doi: 10.1371/journal.pntd.0009076. eCollection 2021 Feb.
Soil-transmitted helminths (STH) are common in low and middle income countries where there is lack of access to clean water and sanitation. Effective diagnosis and treatment are essential for the control of STH infections. However, among STH parasites, Strongyloides stercoralis is the most neglected species, both in diagnostics and control strategies. Diagnostic methods cover different approaches, each with different sensitivities and specificities, such as serology, molecular techniques and microscopy based techniques. Of the later, the Baermann technique is the most commonly used procedure. In the literature, several ways have been described to perform the Baermann method, which illustrates the overall lack of a '(gold) reference standard' method for the diagnosis of S. stercoralis infection. In this study we have evaluated the performance of three Baermann techniques in order to improve the reference standard for the microscopic diagnosis of S. stercoralis infection thereby facilitating individual case detection, mapping of the disease and proper evaluation of treatment responses.
METHODS/PRINCIPAL FINDINGS: A community based cross sectional study was conducted at Zenzelima, Bahir Dar Zuria Ethiopia. A total of 437 stool samples were collected and analyzed by the following procedures: conventional Baermann (CB), modified Baermann (MB), and modified Baermann with charcoal pre-incubation (MBCI). The diagnostic sensitivity and Negative Predictive Value (NPV) of each technique was calculated using the combination of all the three techniques as a composite reference standard. Our result indicated that larvae of S. stercoralis were detected in 151 (34.6%) stool samples. The prevalence of S. stercoralis infection based on the three diagnostic methods was 9.6%, 8.0%, and 31.3% by CB, MB, and MBCI respectively. The sensitivity and NPV for CB, MB, and MBCI were 26.7% and 70.8%, 22.1% and 69.6%, and 87.0% and 93.2%, respectively. The MBCI showed significant difference (P- value = <0.001) in the sensitivity and NPV values when compared with CB and MB values. The agreement between CB, MB, and MBCI with the composite reference standard was 31.8%, 26.7%, 89.6%, respectively.
CONCLUSION/SIGNIFICANCE: Our results suggest the superior performance of MBCI. It is relatively easy to implement, simple to perform and comparatively cheaper. The CB is by far the commonly used method in routine diagnostic although this technique significantly underestimates the true burden of the disease and thereby contributing to the exclusion of S. stercoralis from the control strategies. Therefore, MBCI is recommended as a routine microscopy-based diagnostic test for S. stercoralis infection, particularly in settings where molecular procedures are not available.
土壤传播性蠕虫（STH）在中低收入国家很常见，这些国家缺乏清洁水和卫生设施。有效的诊断和治疗对于控制 STH 感染至关重要。然而，在 STH 寄生虫中，粪类圆线虫是最被忽视的物种，无论是在诊断还是控制策略方面。诊断方法涵盖了不同的方法，每种方法都有不同的敏感性和特异性，例如血清学、分子技术和基于显微镜的技术。在这些方法中，巴氏法是最常用的程序。在文献中，已经描述了几种执行巴氏法的方法，这表明缺乏针对粪类圆线虫感染诊断的“（黄金）参考标准”方法。在本研究中，我们评估了三种巴氏技术的性能，以提高显微镜诊断粪类圆线虫感染的参考标准，从而便于个体病例检测、疾病图谱绘制和治疗反应的正确评估。
方法/主要发现：在埃塞俄比亚巴赫达尔祖里亚的赞泽利马进行了一项社区横断面研究。共采集了 437 份粪便样本，采用以下程序进行分析：常规巴氏法（CB）、改良巴氏法（MB）和改良巴氏法加炭粒预孵育（MBCI）。使用三种技术的组合作为综合参考标准，计算每种技术的诊断敏感性和阴性预测值（NPV）。结果表明，151 份（34.6%）粪便样本中检测到粪类圆线虫幼虫。根据三种诊断方法，粪类圆线虫感染的患病率分别为 CB 法 9.6%、MB 法 8.0%和 MBCI 法 31.3%。CB、MB 和 MBCI 的敏感性和 NPV 分别为 26.7%和 70.8%、22.1%和 69.6%以及 87.0%和 93.2%。与 CB 和 MB 相比，MBCI 的敏感性和 NPV 值差异有统计学意义（P 值均<0.001）。CB、MB 和 MBCI 与综合参考标准的一致性分别为 31.8%、26.7%和 89.6%。
结论/意义：我们的结果表明 MBCI 的性能优越。它相对容易实施、操作简单且价格相对便宜。CB 是目前常规诊断中最常用的方法，尽管这种方法大大低估了疾病的真实负担，从而导致粪类圆线虫被排除在控制策略之外。因此，推荐 MBCI 作为粪类圆线虫感染的常规显微镜诊断检测方法，特别是在无法进行分子检测的情况下。
