Pan-Plasmodium band sensitivity for Plasmodium falciparum detection in combination malaria rapid diagnostic tests and implications for clinical management.

Michelle L Gatton,Jeffrey Glenn,Jane Cunningham,Peter L Chiodini,Qin Cheng,Sandra Incardona,Roxanne R Rees-Channer,Iveth J González,John W Barnwell

doi:10.1186/s12936-015-0629-z

Abstract

BackgroundMalaria rapid diagnostic tests (RDTs) are appropriate for case management, but persistent antigenaemia is a concern for HRP2-detecting RDTs in endemic areas. It has been suggested that pan-pLDH test bands on combination RDTs could be used to distinguish persistent antigenaemia from active Plasmodium falciparum infection, however this assumes all active infections produce positive results on both bands of RDTs, an assertion that has not been demonstrated.MethodsIn this study, data generated during the WHO-FIND product testing programme for malaria RDTs was reviewed to investigate the reactivity of individual test bands against P. falciparum in 18 combination RDTs. Each product was tested against multiple wild-type P. falciparum only samples. Antigen levels were measured by quantitative ELISA for HRP2, pLDH and aldolase.ResultsWhen tested against P. falciparum samples at 200 parasites/μL, 92% of RDTs were positive; 57% of these on both the P. falciparum and pan bands, while 43% were positive on the P. falciparum band only. There was a relationship between antigen concentration and band positivity; ≥4 ng/mL of HRP2 produced positive results in more than 95% of P. falciparum bands, while ≥45 ng/mL of pLDH was required for at least 90% of pan bands to be positive.ConclusionsIn active P. falciparum infections it is common for combination RDTs to return a positive HRP2 band combined with a negative pan-pLDH band, and when both bands are positive, often the pan band is faint. Thus active infections could be missed if the presence of a HRP2 band in the absence of a pan band is interpreted as being caused solely by persistent antigenaemia.

Highlights

Malaria rapid diagnostic tests (RDTs) are appropriate for case management, but persistent antigenaemia is a concern for histidine rich protein 2 (HRP2)-detecting RDTs in endemic areas
Many studies have reported the performance of HRP2 and pLDH-based RDTs for detecting P. falciparum mainly compared to microscopy, as the reference standard [1]
Some studies compare HRP2-detecting RDTs to polymerase chain reaction (PCR) and/or microscopy results to distinguish between persistent antigenaemia, and acute infection; and alternatively, it has been suggested that because pLDH is metabolized after three to five days following anti-malarial therapy, that pan-pLDH test bands on combination RDTs could be used to distinguish between persistent antigenaemia, and active infection [6]

Summary

Introduction

Malaria rapid diagnostic tests (RDTs) are appropriate for case management, but persistent antigenaemia is a concern for HRP2-detecting RDTs in endemic areas. Some studies compare HRP2-detecting RDTs to polymerase chain reaction (PCR) and/or microscopy results to distinguish between persistent antigenaemia, and acute infection; and alternatively, it has been suggested that because pLDH is metabolized after three to five days following anti-malarial therapy, that pan-pLDH test bands on combination RDTs could be used to distinguish between persistent antigenaemia (following treatment), and active infection [6]. This interpretation is contrary to manufacturers’ instructions for HRP2 and pan-pLDH or aldolase-based, combination RDTs, which define a P. falciparum infection as either a single HRP2 test line reaction or both HRP2 and pan-test line reactions. Any modification to manufacturers’ recommendations would only be valid if it can be shown that active infections do not produce the same result (HRP2 test line positive only) as post-treatment antigenaemia

Methods

Results

Conclusion