Clinical Validation of a Commercial LAMP Test for Ruling out Malaria in Returning Travelers: A Prospective Diagnostic Trial

Abstract

The mainstay of malaria diagnosis relies on rapid diagnostic tests (RDTs) and microscopy, both of which lack analytical sensitivity. This leads to repeat testing to rule out malaria. A prospective diagnostic trial of the Meridian illumigene Malaria assay (loop-mediated isothermal amplification [LAMP]) was conducted comparing it with reference microscopy and RDTs (BinaxNOW Malaria) in returning travelers between June 2017 and January 2018. Returning travelers with signs and symptoms of malaria were enrolled in the study. RDTs, microscopy, and LAMP assays were performed simultaneously. A total of 298 patients (50.7% male; mean age, 32.5 years) were enrolled, most visiting friends and relatives (43.3%), presenting with fever (88.9%), not taking prophylaxis (82.9%), and treated as outpatients (84.1%). In the prospective arm (n = 348), LAMP had a sensitivity of 98.1% (95% confidence interval [CI], 90.0%–100%) and a specificity of 97.6% (95% CI, 95.2%–99.1%) vs microscopy. After discrepant resolution with real-time polymerase chain reaction, LAMP had a sensitivity of 100% (95% CI, 93.7%–100%) and a specificity of 100% (95% CI, 98.7%–100%) vs microscopy. After discrepant resolution, RDTs had a sensitivity of 83.3% (95% CI, 58.6%–96.4%) and a specificity of 96.2% (95% CI, 93.2%–98.1%) vs microscopy. When including retrospective specimens (n = 377), LAMP had a sensitivity of 98.8% (95% CI, 93.2%–100%) and a specificity of 97.6% (95% CI, 95.2%–99.1%) vs microscopy, and after discrepant resolution of this set, LAMP had a sensitivity of 100% (95% CI, 95.8%–100%) and a specificity of 100% (95% CI, 98.7%–100%). A cost-benefit analysis of reagents and labor suggests savings of up to USD$13 per specimen using a novel algorithm with LAMP screening.

Evaluation of the colorimetric malachite green loop-mediated isothermal amplification (MG-LAMP) assay for the detection of malaria species at two different health facilities in a malaria endemic area of western Kenya

“…Since NAATs diagnostic methods are more sensitive and have a lower limit of parasite detection than RDTs and microscopy, discrepancies are expected in the results obtained by NAATs and other diagnostic methods. Previous studies have reported a limit of detection of < 6 parasites/µL for NAATs compared to 100-200 parasites/µL for RDTs and 50 parasites/µL for microscopy [12,38]. The sensitivity of MG-LAMP was higher than RDT and microscopy, but a lower specificity at the two health facilities.…”

Diagnosis of malaria in a traveler 9 months after returning from West Africa by illumigene® LAMP assay: A case report

“…Limitations to identify infections with low parasitemia can be overcome by PCR that can detect <5 parasites/μl [8,9,17,18]. LAMP also has an adequate analytical sensitivity to detect low parasite-level parasitemia, compared to PCR [7,10,11].…”

“…The illumigene ® malaria test is a simple and rapid molecular diagnostic test allowing its integration into a 24/7 routine workflow. Because of a simplified sample preparation step and ready-to-use reagents, no technical expertise in molecular biology is needed and the results can be obtained within 1 h. In a recent study, both sensitivity as well as specificity of LAMP was found to be 100% versus microscopy when discrepant results were resolved using PCR [11]. Therefore, the illumigene ® malaria test represents a useful and cost-effective tool for emergency diagnostics [6,7].…”

“…Therefore, the illumigene ® malaria test represents a useful and cost-effective tool for emergency diagnostics [6,7]. Because of its high negative predictive value, it has been suggested that the current test algorithm of three microscopic tests to rule out an infection can be replaced by a single LAMP test, thereby reducing the inconvenience for the patient and saving costs [11].…”

“…The commercially available illumigene ® malaria LAMP assay (Meridian Bioscience/Bioline, Luckenwalde, Germany) is a rapid molecular test for the detection of Plasmodium spp. in venous EDTA whole blood specimens, reaching a sensitivity that is comparable with PCR [11]. In this report, we describe a malaria case caused by P. ovale that would not have been diagnosed without using a molecular screening assay.…”