Banu Sultana Shahana, Ahmed Be-Nazir, Shamsuzzaman Abul Khair Mohammad, Lee Rogan
Parasitology Department, Centre for Infectious Diseases and Microbiology (CIDM), ICPMR, Westmead Hospital, Westmead, NSW, Australia.
Discipline of Medicine, Sydney Medical School, University of Sydney, NSW, Australia.
Parasite Epidemiol Control. 2016 Jul 30;1(3):219-228. doi: 10.1016/j.parepi.2016.07.003. eCollection 2016 Sep.
Definitive diagnosis of visceral leishmaniasis (VL) by demonstrating parasites in tissue smears or by culture involves invasive procedures, technical expertise and adequate laboratory facilities. Endemic countries rely mainly on serological tests to diagnose VL. Currently, the immunochromatographic test incorporating the recombinant K39 antigen (rK39 ICT) is the reference test for rapid diagnosis of VL in the Indian subcontinent. The performance of serological tests using rK39 and other promastigote antigens can vary due to differences in antigen expression, the various hosts and environmental factors. To achieve elimination of VL, diagnostic accuracy will be necessary for active case detection especially in those who carry asymptomatic infections. We evaluated the performance of rK39 ICT, enzyme linked immunosorbent assay using mixed promastigotes from different species (p-ELISA) and indirect fluorescent antibody test (IFAT) utilizing whole promastigotes from the complex for sero-diagnosis of VL in Bangladesh.
The sensitivity of each serological test was evaluated on 155 patients who were diagnosed to have VL by microscopy and/or by culture methods. Test specificities were calculated on 706 healthy blood donors, 91 diagnostic sera from patients with a febrile illness and sera from patients positive for malaria (n = 91) and Chagas disease (n = 91). All statistical calculations were at 95% confidence intervals.
The sensitivities of rK39 ICT, p-ELISA and IFAT were 100%, 86.5% and 92.3%, respectively. All three serological methods had a pooled sensitivity of 82.6%. The specificities of rK39 ICT, p-ELISA and IFAT from combined control groups were 100%, 93.1% and 99.9%, respectively. The respective positive and negative predictive values of the tests were both 100% for rK39 ICT, 66.3% and 97.8% for p-ELISA and 99.3% and 98.8% for IFAT. The p-ELISA showed cross reactivity with 36.3% of sera positive for malaria and 28.6% of sera positive for Chagas disease while rK39 ICT and IFAT showed no cross reactivity.
This study confirms the efficiency of rK39 ICT for rapid diagnosis of VL. The p-ELISA using mixed promastigote antigens did not perform well as a serological test for VL in Bangladesh. Due to high sensitivity and specificity of whole promastigote antigen of complex utilized in IFAT, this test can be considered in combination with rK39 ICT to confirm VL diagnosis when clinical diagnosis cannot distinguish between other diseases.
通过在组织涂片或培养物中发现寄生虫来明确诊断内脏利什曼病（VL），需要采用侵入性操作、专业技术以及完善的实验室设施。流行国家主要依靠血清学检测来诊断VL。目前，采用重组K39抗原的免疫层析试验（rK39 ICT）是印度次大陆快速诊断VL的参考检测方法。由于抗原表达、宿主种类和环境因素的差异，使用rK39和其他前鞭毛体抗原的血清学检测性能可能会有所不同。为实现消除VL的目标，对于主动病例检测，尤其是无症状感染者，诊断准确性至关重要。我们评估了rK39 ICT、使用来自不同物种的混合前鞭毛体的酶联免疫吸附测定（p-ELISA）以及利用该复合体的全前鞭毛体进行间接荧光抗体试验（IFAT）在孟加拉国对VL进行血清学诊断的性能。
对155例经显微镜检查和/或培养方法确诊为VL的患者，评估每种血清学检测的敏感性。在706名健康献血者、91份发热性疾病患者的诊断血清以及疟疾阳性患者（n = 91）和恰加斯病阳性患者（n = 91）的血清中计算检测特异性。所有统计计算均在95%置信区间进行。
rK39 ICT、p-ELISA和IFAT的敏感性分别为100%、86.5%和92.3%。这三种血清学方法的合并敏感性为82.6%。联合对照组中rK39 ICT、p-ELISA和IFAT的特异性分别为100%、93.1%和99.9%。rK39 ICT检测的阳性预测值和阴性预测值均为100%，p-ELISA分别为66.3%和97.8%，IFAT分别为99.3%和98.8%。p-ELISA与36.3%的疟疾阳性血清和28.6%的恰加斯病阳性血清有交叉反应，而rK39 ICT和IFAT无交叉反应。
本研究证实了rK39 ICT对VL快速诊断的有效性。在孟加拉国，使用混合前鞭毛体抗原的p-ELISA作为VL的血清学检测方法表现不佳。由于IFAT中使用的该复合体全前鞭毛体抗原具有高敏感性和特异性，当临床诊断无法区分其他疾病时，可考虑将该检测与rK39 ICT联合使用以确诊VL。
