Vallejo Andrés F, Martínez Nora L, González Iveth J, Arévalo-Herrera Myriam, Herrera Sócrates
Caucaseco Scientific Research Center, Cali, Colombia.
Foundation for Innovative New Diagnostics (FIND), Geneva, Switzerland.
PLoS Negl Trop Dis. 2015 Jan 8;9(1):e3453. doi: 10.1371/journal.pntd.0003453. eCollection 2015 Jan.
Most commonly used malaria diagnostic tests, including microscopy and antigen-detecting rapid tests, cannot reliably detect low-density infections which are frequent in low transmission settings. Molecular methods such as polymerase chain reaction (PCR) are highly sensitive but remain too laborious for field deployment. In this study, the applicability of a malaria diagnosis kit based on loop-mediated isothermal amplification (mLAMP) was assessed in malaria endemic areas of Colombia with Plasmodium vivax predominance.
METHODOLOGY/PRINCIPAL FINDINGS: First, a passive case detection (PCD) study on 278 febrile patients recruited in Tierralta (department of Cordoba) was conducted to assess the diagnostic performance of the mLAMP method. Second, an active case detection (ACD) study on 980 volunteers was conducted in 10 sentinel sites with different epidemiological profiles. Whole blood samples were processed for microscopic and mLAMP diagnosis. Additionally RT-PCR and nested RT-PCR were used as reference tests. In the PCD study, P. falciparum accounted for 23.9% and P. vivax for 76.1% of the infections and no cases of mixed-infections were identified. Microscopy sensitivity for P. falciparum and P. vivax were 100% and 86.1%, respectively. mLAMP sensitivity for P. falciparum and P. vivax was 100% and 91.4%, respectively. In the ACD study, mLAMP detected 65 times more cases than microscopy. A high proportion (98.0%) of the infections detected by mLAMP was from volunteers without symptoms.
CONCLUSIONS/SIGNIFICANCE: mLAMP sensitivity and specificity were comparable to RT-PCR. LAMP was significantly superior to microscopy and in P. vivax low-endemicity settings and under minimum infrastructure conditions, it displayed sensitivity and specificity similar to that of single-well RT-PCR for detection of both P. falciparum and P. vivax infections. Here, the dramatically increased detection of asymptomatic malaria infections by mLAMP demonstrates the usefulness of this new tool for diagnosis, surveillance, and screening in elimination strategies.
包括显微镜检查和抗原检测快速检测在内的大多数常用疟疾诊断测试，无法可靠地检测出在低传播环境中常见的低密度感染。诸如聚合酶链反应（PCR）等分子方法高度灵敏，但对于现场应用而言仍过于繁琐。在本研究中，在哥伦比亚间日疟原虫占主导的疟疾流行地区评估了基于环介导等温扩增技术（mLAMP）的疟疾诊断试剂盒的适用性。
方法/主要发现：首先，对在蒂拉尔塔（科尔多瓦省）招募的278名发热患者进行了被动病例检测（PCD）研究，以评估mLAMP方法的诊断性能。其次，在10个具有不同流行病学特征的哨点对980名志愿者进行了主动病例检测（ACD）研究。对全血样本进行显微镜检查和mLAMP诊断处理。此外，将逆转录PCR（RT-PCR）和巢式逆转录PCR用作参考检测方法。在PCD研究中，恶性疟原虫感染占23.9%，间日疟原虫感染占76.1%，未发现混合感染病例。显微镜检查对恶性疟原虫和间日疟原虫的敏感性分别为100%和86.1%。mLAMP对恶性疟原虫和间日疟原虫的敏感性分别为100%和91.4%。在ACD研究中，mLAMP检测出的病例数比显微镜检查多65倍。mLAMP检测出的感染病例中，很大一部分（98.0%）来自无症状志愿者。
结论/意义：mLAMP的敏感性和特异性与RT-PCR相当。环介导等温扩增技术（LAMP）明显优于显微镜检查，并且在间日疟原虫低流行地区以及最低基础设施条件下，其检测恶性疟原虫和间日疟原虫感染的敏感性和特异性与单孔RT-PCR相似。在此，mLAMP对无症状疟疾感染的检测大幅增加证明了这一新型工具在消除疟疾策略中的诊断、监测和筛查方面的有用性。
