Diagnostic performance of the loop-mediated isothermal amplification (LAMP) based illumigene® malaria assay in a non-endemic region

Abstract

BackgroundLight microscopy and antigen-based rapid diagnostic tests are the primary diagnostic tools for detecting malaria, although being labour-intensive and frequently challenged by lack of personnel’s experience and low levels of parasite density. The latter being especially important in non-endemic settings. Novel molecular techniques aim to overcome this drawback. The objective of this study was to assess the diagnostic performance of the illumigene malaria assay® (Meridian Bioscience) compared to microscopy, RDT and real-time PCR. This loop-mediated isothermal amplification (LAMP) assay is a qualitative in vitro diagnostic test for the direct detection of Plasmodium spp. DNA in human venous whole blood samples.MethodsThe illumigene assay was assessed on a retrospective panel of stored blood samples (n = 103) from returned travellers and external quality control samples (n = 12). Additionally the assay was prospectively assessed on 30 fresh routine samples with a request for malaria diagnosis. The illumigene assay was compared to microscopy, RDT and Plasmodium species specific real-time PCR.ResultsIn the retrospective evaluation, the illumigene assay showed 100% agreement with the real-time PCR, RDT and microscopy yielding a sensitivity and specificity of 100% (95% CI 95.1–100% and 89.7–100%, respectively). Seven samples from patients recently treated for Plasmodium falciparum infection that were RDT positive and microscopy negative yielded positive test results. The performance of the illumigene assay equals that of microscopy combined with RDT in the prospective panel with three false negative RDT results and one false negative microscopy result. Excellent concordance with PCR was observed. The limit of detection of the assay approached 0.5 parasites/µL for both P. falciparum and Plasmodium vivax.ConclusionIn non-endemic regions where the diagnostic process for malaria infections is questioned by lack of experience and low levels of parasite densities, the illumigene assay can be of value. Due to its high sensitivity, the LAMP assay may be considered as primary diagnostic test. The results of this study indicate that negative screen results do not need further confirmation. However, before implementation, this approach needs to be confirmed in larger, prospective studies. A shortcoming of this assay is that no species identification nor determination of parasite density are possible.

Reactivation of Plasmodium infection during a treatment with infliximab: A case report

“…This is a qualitative test, performed more rapidly (30 0 ) than the classic microscopic method (90 0 ). In comparison to PCR with similar sensitivity, the LAMP is easier to implement and less expensive especially because it does not require expensive thermal cyclers, specially equipped rooms, specialized operators or batch testing (Koninck et al, 2017). This test can detect very low parasitemias but not the dormant blood stage forms.…”

Evaluation of Visual LAMP detection of Plasmodium falciparum and non-Plasmodium falciparum

“…The WHO external assessment of the malaria parasite's mirror test capacity in China showed that the correct rates of negative, Plasmodium falciparum (P.f),, Plasmodium vivax (P.v) were 92.5%, 78.3%, 70.8% respectively [20] . RDT is facilitate and fast, with detection limit of 100 plasmids/ μl [19,21] . It shows high sensitivity to plasmid infections of more than 100 plasmids/μl(median 94.3%), sensitivity of which decrease significantly with a density of less than 100 plasmids/μl (median 74.1%) [21] .…”

“…RDT is facilitate and fast, with detection limit of 100 plasmids/ μl [19,21] . It shows high sensitivity to plasmid infections of more than 100 plasmids/μl(median 94.3%), sensitivity of which decrease significantly with a density of less than 100 plasmids/μl (median 74.1%) [21] . Meantime it shows limited sensitivity when detecting low-density infection [16,22] , and less sensitivity to non-P.f P.v as 66.0-88.0%, P.o as 5.5-86.7%, P.m as 21.4-45.2% [19] .…”

Multiplex real-time PCR for diagnosing malaria in a non-endemic setting: a prospective comparison to conventional methods

“…Still, despite the high negative predictive value of molecular testing, the majority of laboratories in nonendemic settings do not use PCR as a first line diagnosis for all their malaria suspected cases. This attitude toward molecular diagnosis of imported malaria might change rapidly in the coming years with the introduction of simplified test procedures, such as the Illumigene loopmediated isothermal amplification (LAMP) malaria assay, which makes it possible to perform molecular diagnostic testing 24/7 without the need of advanced laboratory equipment or high levels of expertise [8]. Preferably these tests have a quantitative output and can differentiate Plasmodium parasites at species level.…”

“…Although not widely used as a routine diagnostic tool in a clinical setting, nucleic acid amplification testing (NAAT) for the detection of Plasmodium DNA can be performed either by using real-time PCR or loopmediated isothermal amplification (LAMP) [8,9]. NAAT provides a limit of detection that is at least tenfold better than an experienced microscopist, and improved detection of mixed infections.…”