We thank all trial subjects for their participation in this study. We also thank K. Suijk-Benschop, J. Fehrmann-Naumann, C. Prins, E. Jonker, G. Hardeman and S. ten Velden-Schipper for blood collection and care for the subjects, the LUMC department of Medical Microbiology for facilitating parasitological diagnosis and M. Erkens, T. Arens, J. van der Slot, H. Gerritsma, F. van de Sande, J. van Schie, E. Brienen, J. Schelfaut, J. Verweij, J. Kromhout, E. van Oorschot and M. Beljon for reading thick smears. We thank M. Bootsma for cardiac monitoring of the trial subjects, W. Graumans and R. Siebelink-Stoter for culturing parasites J. Klaassen, L. Pelser-Posthumus, J. Kuhnen, A. Pouwelsen and Geert-Jan van Ge- mert for generating infected mosquitoes and assistance with immunizing and challenging subjects, J. Wiersma for assistance with the challenge. We thank the members of the Safety Monitoring Committee, J.A. Romijn, M. de Boer and M. Laurens.
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*Contributed equally Malaria Journal. 2016 Aug 5;15(1):398.
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ABSTRACT
Background
Controlled human malaria infection (CHMI) has become well-established in the evaluation of drugs and vaccines. Anti-malarial treatment is usually initiated when thick blood smears are positive by microscopy. This study explores the effects of using the more sensitive qPCR as the primary diagnostic test.
Methods
1,691 diagnostic blood samples were analysed by microscopy and qPCR from 115 volunteers (55 malaria naïve and 60 having received Chemoprophylaxis and Sporozoite immunization) who were challenged by five mosquitoes infect- ed with Plasmodium falciparum sporozoites of the NF54 strain.
Results
Retrospective analysis of different qPCR criteria for diagnosis and treatment, showed that once daily qPCR (threshold 100 parasites/ml) had 99% sensitivity and 100% specificity, shortened the median prepatent period from 10.5 to 7.0 days after CHMI when compared to twice daily measurement of thick blood smears (threshold 4,000 parasites/ml). This is expected to result in a 78% de- crease of adverse events before initiation of treatment in future studies. Trial outcome related to infection and protective efficacy remained unchanged.
Conclusion
The use of qPCR as primary diagnostic test in CHMI decreases symptoms as well as parasitaemia while obviating the need for twice daily follow-up. The implementation improves safety while reducing the clinical burden and costs without compromising the evaluation of protective efficacy.