Quantification of malaria antigens PfHRP2 and pLDH by quantitative suspension array technology in whole blood, dried blood spot and plasma

Abstract

BackgroundMalaria diagnostics by rapid diagnostic tests (RDTs) relies primarily on the qualitative detection of Plasmodium falciparum histidine-rich protein 2 (PfHRP2) and Plasmodium sp lactate dehydrogenase (pLDH). As novel RDTs with increased sensitivity are being developed and implemented as point of care diagnostics, highly sensitive laboratory based assays are needed for evaluating RDTs performance. Here, a quantitative suspension array technology (qSAT) was developed, validated and applied for the simultaneous detection of PfHRP2 and pLDH in a variety of clinical samples (whole blood, plasma and dried blood spots) from different endemic countries.ResultsThe qSAT was specific for the target antigens, with analytical ranges of 6.8 to 762.8 pg/ml for PfHRP2 and 78.1 to 17076.6 pg/ml for P. falciparum (Pf-LDH). The assay detected P. vivax LDH (Pv-LDH) at a lower sensitivity than Pf-LDH (analytical range of 1093.20 to 187288.5 pg/ml). Both PfHRP2 and pLDH levels determined using the qSAT showed to positively correlate with parasite densities determined by quantitative PCR (Spearman r=0.59 and 0.75, respectively) as well as microscopy (Spearman r=0.40 and 0.75, respectively), suggesting the assay to be a good predictor of parasite density.ConclusionThis immunoassay can be used as a reference test for the detection and quantification of PfHRP2 and pLDH, and could serve for external validation of RDTs performance, to determine antigen persistence after parasite clearance, as well as a complementary tool to assess malaria burden in endemic settings.

Parasitaemia and fever in uncomplicated Plasmodium vivax malaria: a systematic review and individual patient data meta-analysis

“…Our analysis also assumed that patients enrolled in the original studies presented with an initial infection, however, they may have presented with a relapsing episode of malaria. Finally, current P. vivax RDTs detect parasite antigen concentration (Plasmodium lactate dehydrogenase, pLDH) rather than parasite density, although pLDH concentration and parasitaemia have been shown to be well-correlated (40).…”

Malaria und ihre Bedeutung in der Reisemedizin

“…HRP2-basierte RDTs können daher nicht zur Therapiekontrolle eingesetzt werden. Sie haben auch bei Personen, die eine (partielle) Malaria-Chemoprophylaxe eingenommen haben, u. U. eine nur eingeschränkte Aussagekraft 12 . Im Gegensatz zu HRP2 persistiert pLDH nach der Parasiten-Clearance nicht im Blut.…”