Discussion

Introduction and methods: Screening for malaria infection in travelers with fever by conventional microscopy requires qualified technicians. As most patients test negative, screening by a point of care method like the Illumigene LAMP Plasmodium assay (Meridian Bioscience, London, UK) will reduce the need for qualified technicians. This study describes the performance of the Illumigene LAMP malaria assay in 1) samples of 12 volunteers participating in a protocol of controlled experimental malaria infections (CHMI) and tested by qPCR, and 2) samples from n≤7 Plasmodium falciparum positive travelers, stored at -80^oC at the Radboudumc. The latter were tested by conventional microscopy (QBC (Drucker diagnostics, Port Matilda, USA) and thick smear). Results: Of 78 CHMI samples tested, n≤50 (64%) and n≤41 (53%) tested positive by respectively qPCR and Illumigene LAMP malaria assay. Compared to qPCR the sensitivity and specificity of Illumigene was 76% and 89% respectively. The density threshold for 100% positivity in this population was 676 parasites/ml. In travelers the Illumigene tested positive in 7/7 cases. The thresholds were 1-5 *10³ parasites/ml for the QBC, 5 *10³ parasites/ml for thick smear and 1 *10³ parasites/ml for Illumigene respectively. The Illumigene tested positive up to 7 days longer after successful treatment compared to conventional microscopic analysis. Conclusion: Illumigene LAMP malaria assay performed well as first screening for P. falciparum, but shows prolonged positivity post-treatment.