Laboratório de Soroepidemiologia e Imunobiologia, Instituto de Medicina Tropical da Faculdade de Medicina, Universidade de São Paulo, SP, Brazil.
Departamento de Doenças Infecciosas e Parasitárias, Faculdade de Medicina, Universidade de São Paulo, SP, Brazil.
PLoS One. 2020 Apr 2;15(4):e0230610. doi: 10.1371/journal.pone.0230610. eCollection 2020.
The development of rK39-based immunochromatographic rapid diagnostic tests represents an important advance for serodiagnosis of visceral leishmaniasis, being cheap and easy to use at the point of care (POC). Although the use of rK39 have considerably improved the sensitivity and specificity of serological tests compared with total antigens, great variability in sensitivity and specificity was reported. This study aimed at the evaluation of "Kalazar Detect™ Rapid Test, Whole Blood" (Kalazar Detect RDT) for Visceral Leishmaniasis (VL) diagnosis using oral fluid, whole blood and serum specimens collected at different endemic areas of VL of Brazil.
To evaluate Kalazar Detect RDT, oral fluid, whole blood and serum specimens from 128 VL patients, 85 healthy individuals, 22 patients with possible cross-reactivity diseases and 20 VL/aids coinfected patients were collected and assayed at the POC.
The performance of Kalazar Detect RDT in whole blood and serum was similar; however, using oral fluid, the sensitivity was low. Particularly in samples from the city of Natal, Rio Grande do Norte state in Northeastern Brazil, we observed low sensitivity, 80.0% (95% CI: 62.7-90.5), using whole blood and serum, and poor sensitivity, 43.3% (95% CI: 27.4-60.8) with oral fluid. Those values were much lower than in the other regions, where sensitivity ranged from 92.7-96.3% in whole blood and serum, and 80.0-88.9% in oral fluid. Besides, in VL/aids coinfected patients, lower sensitivity was achieved compared with VL patients. In samples from Natal, the sensitivity was 0.0% (95% CI: 0.0-49.0) and 25.0% (95% CI: 4.6-69.9), using oral fluid and serum/whole blood, respectively; in samples from the other regions, the sensitivity ranged from 40.0-63.6% and 80.0-81.8%, respectively. As for specificity, high values were observed across the fluids, 100.0% (95% CI: 96.5-100.0) in whole blood, 96.3% (95% CI: 90.8-98.5) in serum, and 95.3% (95% CI: 89.5-98.0) in oral fluid; across localities, specificity ranged from 85.7-100.0%. Serum samples sent by the collaborating centers to Instituto de Medicina Tropical (n = 250) were tested by Kalazar Detect RDT, Direct Agglutination Test, Indirect immunofluorescence assay, Enzyme-linked immunosorbent assay, and IT-Leish® RDT. The regional difference in the performance of rK39-based RDT and lower sensitivity in Leishmania/HIV coinfected patients raise concern on the routine use of these products for the diagnosis of VL.
rK39 为基础的免疫层析快速诊断测试的发展代表了内脏利什曼病血清学诊断的重要进展，因为它在护理点（POC）既便宜又易于使用。尽管 rK39 的使用与总抗原相比大大提高了血清学检测的灵敏度和特异性，但报道的灵敏度和特异性差异很大。本研究旨在评估“Kalazar Detect™快速检测，全血”（Kalazar Detect RDT）在巴西不同内脏利什曼病流行地区采集的口服液、全血和血清样本中的内脏利什曼病（VL）诊断。
在 POC 处对 128 例 VL 患者、85 名健康个体、22 例可能具有交叉反应性疾病的患者和 20 例 VL/aids 合并感染的患者的口服液、全血和血清样本进行了 Kalazar Detect RDT 评估。
Kalazar Detect RDT 在全血和血清中的性能相似；然而，在使用口服液时，灵敏度较低。特别是在巴西东北部北里奥格兰德州纳塔尔市的样本中，我们观察到使用全血和血清的灵敏度较低，为 80.0%（95%CI：62.7-90.5），而使用口服液的灵敏度较低，为 43.3%（95%CI：27.4-60.8）。这些值远低于其他地区，全血和血清的灵敏度范围为 92.7-96.3%，口服液的灵敏度范围为 80.0-88.9%。此外，在 VL/aids 合并感染的患者中，与 VL 患者相比，灵敏度较低。在纳塔尔的患者样本中，口服液和血清/全血的灵敏度分别为 0.0%（95%CI：0.0-49.0）和 25.0%（95%CI：4.6-69.9）；在其他地区的样本中，灵敏度范围为 40.0-63.6%和 80.0-81.8%。至于特异性，所有液体的特异性均较高，全血为 100.0%（95%CI：96.5-100.0），血清为 96.3%（95%CI：90.8-98.5），口服液为 95.3%（95%CI：89.5-98.0）；在不同地区，特异性范围为 85.7-100.0%。来自合作中心的 250 份血清样本通过 Kalazar Detect RDT、直接凝集试验、间接免疫荧光法、酶联免疫吸附试验和 IT-Leish® RDT 进行了检测。rK39 为基础的 RDT 在性能上的地区差异和利什曼原虫/艾滋病毒合并感染患者的灵敏度较低引起了人们对这些产品在 VL 诊断中的常规使用的关注。
