Field implementation and evaluation of novel isothermal, nucleic acid–based diagnostic tools for malaria elimination in sub Saharan Africa

Cheryll Eniyou Oriero

Research output: ThesisDoctoral dissertation - Doctoral dissertation

Abstract

Malaria transmission occurs in all six World Health Organization (WHO) regions, with an estimated 3.2 billion people in 97 countries and territories at risk of being infected and developing disease in 2013. Currently used diagnostic tests, microscopy and rapid diagnostic tests (RDTs), do not accurately detect low-density and asymptomatic infections, which contribute to disease transmission. Molecular methods such as polymerase chain reaction (PCR) that can detect low-density infections are expensive and too complex to use in resource-limited settings. Thus, the less complex isothermal amplification methods were developed. The aim of this project was to develop a novel isothermal assay with high diagnostic accuracy comparable to PCR using novel targets and evaluate it in the field as part of the tools towards malaria elimination. The Apicoplast genome target in a loop-mediated isothermal amplification (LAMP) assay, showed comparable results with a standard PCR assay. Using laboratory strains and 184 archived DNA samples, limit of detection (LOD) of the novel LAMP assay was approximately 2 parasites/µL, with sensitivity of 98%, specificity of 91% and Cohen’s kappa coefficient of 0.9. Deploying it with currently used tools (microscopy and RDT) in a field setting, in comparison with a reference PCR method, the LAMP assay had a sensitivity of 92% while microscopy and RDT had 78% and 76%, respectively. Specificity was 97% for LAMP, 99% for microscopy, and 88% for RDT. Area under the receiver operating characteristic (ROC) curve was 0.94 for LAMP, 0.88 for microscopy and 0.81 RDT. Turn-around-time for the LAMP assay was approximately 3.5hours for an average of 27 ± 9.5 samples collected daily, compared to a minimum of 10 samples/hour per operator by RDT and over eight hours by microscopy. The novel LAMP assay is high throughput, processing large numbers of samples within a shorter time than the current gold standard. It also showed better agreement than RDT when compared with PCR, thus it could be used in active case detection intervention programs, which are currently being explored to support malaria elimination.
Original languageEnglish
Place of PublicationAntwerp
Publisher
Electronic ISBNs9781339550558
Publication statusPublished - 2015

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