First Field Evaluation of Novel LDH- and HRP2-based Rapid Tests for Plasmodium vivax and Plasmodium falciparum Malaria Diagnosis
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Background
Rapid diagnostic tests (RDTs) are crucial for malaria diagnosis. Where Plasmodium falciparum and Plasmodium vivax are co-endemic, and where P. falciparum hrp2 / 3 deletions are frequent, RDTs need to detect either species, and P. falciparum using additional antigens to HRP2, such as LDH.
Methods
Clinical patients presenting for malaria diagnosis in southern Ethiopia were enrolled and tested by microscopy at the health center and by four different RDTs: (i) BIOCREDIT Malaria Ag Pf (cHL) with a line combining HRP2 and LDH for P. falciparum , (ii) BIOCREDIT Malaria Ag Pf/Pv (cHL/L) with one line combining HRP2 and LDH for P. falciparum and one with LDH for P. vivax , (iii) Bioline Malaria Ag Pf/Pf/Pv with separate lines for HRP2 and LDH for P. falciparum , and LDH for P. vivax , and (iv) First Response with an HRP2 line for P. falciparum and a LDH line for P. vivax . The two BIOCREDIT RDTs had not previously been tested in the field. qPCR and expert microscopy were conducted as reference tests. P. falciparum positive samples were typed for hrp2 / 3 deletion.
Results
Among 708 patients included in the final analysis, 46.0% were positive by qPCR (77 P. falciparum mono-infections, 198 P. vivax mono-infections, and 51 mixed infections). Strong agreement was observed between results of the different RDTs, with no significant differences in sensitivity. At densities >20 parasites/µL by qPCR, all RDTs reached sensitivities of >96% for P. falciparum , compared to 63% by health center microscopy, and for P. vivax all RDTs reached sensitivities of >92%, compared to 72% by health center microscopy. Specificity was >99% for all P. falciparum RDTs and >98% for all P. vivax RDTs. Only two P. falciparum infections carried hrp2 and hrp3 deletions, both were detected by all LDH-based RDTs.
Conclusions
Use of RDTs improves diagnostic accuracy compared to microscopy. The novel BIOCREDIT and Bioline RDTs show high sensitivity and specificity for P. falciparum and P. vivax diagnosis.
