Assessment of Plasmodium antigens and CRP in dried blood spots with multiplex malaria array

Ihn Kyung Jang,Warat Haohankhunnatham,Maxwell Murphy,Sara Aranda,Andrew Rashid,Stephane Proux,Gonzalo J Domingo,Mallika Imwong,John C Rek,Harriet Adrama,Rebecca Barney,Xavier C Ding,Muhammad Helwany,François Nosten,Bryan Greenhouse,Dionicia Gamboa,Emmanuel Arinaitwe

doi:10.1007/s12639-020-01325-2

Abstract

Dried blood spots (DBS) typically prepared on filter papers are an ideal sample type for malaria surveillance by offering easy and cost-effective methods in terms of sample collection, storage, and transport. The objective of this study was to evaluate the applicability of DBS with a commercial multiplex malaria assay, developed to concurrently measure Plasmodium antigens, histidine-rich protein 2 (HRP2), Plasmodium lactate dehydrogenase (pLDH), and a host inflammatory biomarker, C-reactive protein (CRP), in whole blood. The assay conditions were optimized for DBS, and thermal stability for measurement of Plasmodium antigens and CRP in dried blood were determined. Performance of the multiplex assay on matched DBS and whole blood pellet samples was also evaluated using the clinical samples. The results indicate the acceptable performance in multiplex antigen detection using DBS samples. At cutoff levels for DBS, with a diagnostic specificity with a lower 95% confidence bound > 92%, diagnostic sensitivities against polymerase chain reaction (PCR)–confirmed malaria for HRP2, Pf LDH, Pv LDH, and Pan LDH were 93.5%, 80.4%, 21.3%, and 55.6%, respectively. The half-life of pLDH was significantly less than that of HRP2 in thermal stability studies. Results with DBS samples collected from Peru indicate that the uncontrolled storage conditions of DBS can result in inaccurate reporting for infection with P. falciparum parasites with hrp2/3 deletions. With careful consideration that minimizing the unfavorable DBS storage environment is essential for ensuring integrity of heat-labile Plasmodium antigens, DBS samples can be used as an alternative to liquid whole blood to detect P. falciparum with hrp2/3 deletions in malaria surveillance.

Highlights

Malaria is currently estimated to infect around 219 million individuals, resulting in 435,000 deaths each year (World Health Organization 2018)
The objective of this study was to evaluate the applicability of Dried blood spots (DBS) with a commercial multiplex malaria assay, developed to concurrently measure Plasmodium antigens, histidine-rich protein 2 (HRP2), Plasmodium lactate dehydrogenase, and a host inflammatory biomarker, C-reactive
Given these restrictions associated with HRP2, rapid diagnostic test (RDT) identifying P. falciparum with hrp2/3 deletions and other Plasmodium species are needed in areas where infections with hrp2/3 deletion mutants and other species are prevalent

Summary

Introduction

Malaria is currently estimated to infect around 219 million individuals, resulting in 435,000 deaths each year (World Health Organization 2018). All HRP2based RDTs, which recognize a homolog of HRP2, HRP3 as well and are most widely used in Africa, can give false negative results when applied to infections with P. falciparum parasites with a partial or complete deletion of hrp and hrp (Pati et al 2018; Kumar et al 2013). Given these restrictions associated with HRP2, RDTs identifying P. falciparum with hrp2/3 deletions and other Plasmodium species are needed in areas where infections with hrp2/3 deletion mutants and other species are prevalent. PLDH carrying both species-specific and Pan-specific epitopes can allow identification of these hrp2/3 deletion mutants of P. falciparum and differentiate two major species and all Plasmodium species (Hurdayal et al 2010)

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Conclusion