Singh Ruchi, Singh Dhirendra Pratap, Savargaonkar Deepali, Singh Om P, Bhatt Rajendra M, Valecha Neena
National Institute of Malaria Research (ICMR), Dwarka; National Institute of Pathology (ICMR), Safdarjung Hospital Campus, New Delhi, India.
National Institute of Malaria Research (ICMR), Dwarka, India.
J Vector Borne Dis. 2017 Jan-Mar;54(1):54-60.
BACKGROUND & OBJECTIVES: Loop-mediated isothermal amplification (LAMP) is an emerging nucleic acid based diag- nostic approach that is easily adaptable to the field settings with limited technical resources. This study was aimed to evaluate the LAMP assay for the detection and identification of Plasmodium falciparum and P. vivax infection in malaria suspected cases using genus and species-specific assay.
The 18S rRNA-based LAMP assay was evaluated for diagnosis of genus Plasmodium, and species- specific diagnosis of P. falciparum and P. vivax, infection employing 317 malaria suspected cases, and the results were compared with those obtained by 18S nested PCR (n-PCR). All the samples were confirmed by microscopy for the presence of Plasmodium parasite.
The n-PCR was positive in all Plasmodium-infected cases (n=257; P. falciparum=133; P. vivax=124) and negative in microscopy negative cases (n=58) except for two cases which were positive for P. vivax, giving a sen- sitivity of 100% (95% CI: 97.04-100%) and a specificity of 100% (95% CI: 88.45-99.5%). Genus-specific LAMP assay missed 11 (3.2%) microscopy and n-PCR confirmed vivax malaria cases. Considering PCR results as a refer- ence, LAMP was 100% sensitive and specific for P. falciparum, whereas it exhibited 95.16% sensitivity and 96.7% specificity for P. vivax. The n-PCR assay detected 10 mixed infection cases while species-specific LAMP detected five mixed infection cases of P. vivax and P. falciparum, which were not detected by microscopy.
INTERPRETATION & CONCLUSION: Genus-specific LAMP assay displayed low sensitivity. Falciparum specific LAMP assay displayed high sensitivity whereas vivax specific LAMP assay displayed low sensitivity. Failed detection of vivax cases otherwise confirmed by the n-PCR assay indicates exploitation of new targets and improved detection methods to attain 100% results for P. vivax detection.
环介导等温扩增技术（LAMP）是一种新兴的基于核酸的诊断方法，易于在技术资源有限的现场环境中应用。本研究旨在评估LAMP检测法，通过属特异性和种特异性检测，对疑似疟疾病例中的恶性疟原虫和间日疟原虫感染进行检测和鉴定。
采用基于18S rRNA的LAMP检测法，对317例疑似疟疾病例进行疟原虫属诊断以及恶性疟原虫和间日疟原虫感染的种特异性诊断，并将结果与18S巢式PCR（n-PCR）结果进行比较。所有样本均通过显微镜检查疟原虫的存在情况进行确认。
n-PCR在所有疟原虫感染病例（n = 257；恶性疟原虫 = 133；间日疟原虫 = 124）中均呈阳性，在显微镜检查阴性的病例（n = 58）中除两例间日疟原虫阳性外均为阴性，敏感性为100%（95%CI：97.04 - 100%），特异性为100%（95%CI：88.45 - 99.5%）。属特异性LAMP检测法漏检了11例（3.2%）经显微镜检查和n-PCR确认的间日疟病例。以PCR结果为参照，LAMP对恶性疟原虫的敏感性和特异性均为100%，而对间日疟原虫的敏感性为95.16%，特异性为96.7%。n-PCR检测到10例混合感染病例，而种特异性LAMP检测到5例显微镜检查未检出的间日疟原虫和恶性疟原虫混合感染病例。
属特异性LAMP检测法敏感性较低。恶性疟原虫特异性LAMP检测法敏感性较高，而间日疟原虫特异性LAMP检测法敏感性较低。n-PCR检测法确认的间日疟病例未被检测到，表明需要开发新的靶点和改进检测方法，以实现间日疟原虫检测100%的结果。
