Abstract
BackgroundThe rapid diagnostic tests for malaria (RDT) constitute a fast and opportune alternative for non-complicated malaria diagnosis in areas where microscopy is not available. The objective of this study was to validate a RDT named Parascreen™ under field conditions in Iquitos, department of Loreto, Peru. Parascreen™ is a RDT that detects the histidine-rich protein 2 (HRP2) antigen from Plasmodium falciparum and lactate deshydrogenase from all Plasmodium species.MethodsParascreen™ was compared with microscopy performed by experts (EM) and polymerase chain reaction (PCR) using the following indicators: sensitivity (Se), specificity (Sp), positive (PV+) and negative predictive values (PV-), positive (LR+) and negative likehood ratio (LR-).Results332 patients with suspected non-complicated malaria who attended to the MOH health centres were enrolled between October and December 2006. For P. falciparum malaria, Parascreen™ in comparison with EM, had Se: 53.5%, Sp: 98.7%, PV+: 66.7%, PV-: 97.8%, LR+: 42.27 and LR-: 0.47; and for non-P. falciparum malaria, Se: 77.1%, Sp: 97.6%, PV+: 91.4%, PV-: 92.7%, LR+: 32.0 and LR-: 0.22. The comparison of Parascreen™ with PCR showed, for P. falciparum malaria, Se: 81.8%, Sp: 99.1%, PV+: 75%, PV-: 99.4, LR+: 87.27 and LR-: 0.18; and for non-P. falciparum malaria Se: 76.1%, Sp: 99.2%, PV+: 97.1%, PV-: 92.0%, LR+: 92.51 and LR-: 0.24.ConclusionsThe study results indicate that Parascreen™ is not a valid and acceptable test for malaria diagnosis under the field conditions found in the Peruvian Amazon. The relative proportion of Plasmodium species, in addition to the genetic characteristics of the parasites in the area, must be considered before applying any RDT, especially after the finding of P. falciparum malaria parasites lacking pfhrp2 gene in this region.
Highlights
The rapid diagnostic tests for malaria (RDT) constitute a fast and opportune alternative for noncomplicated malaria diagnosis in areas where microscopy is not available
Even though the RDT was of simple training and use for the local health staff, it showed variable indicators when compared with expert microscopy (EM) and polymerase chain reaction (PCR), depending on the Plasmodium species (P. vivax or P. falciparum) and parasitaemia of the infections
In comparison with other RDTs, ParascreenTM sensitivity for P. falciparum infection was lower than that obtained with OptiMALTM which detects Plasmodium lactate deshydrogenase
Summary
The rapid diagnostic tests for malaria (RDT) constitute a fast and opportune alternative for noncomplicated malaria diagnosis in areas where microscopy is not available. Despite a reduction of the incidence by up to 40% during the last four years in Peru, malaria due to Plasmodium falciparum and Plasmodium vivax remains an important public health problem, especially in the Amazon region where more than 70% of the cases of the country are reported [2]. The established method for laboratory confirmation of malaria, presents technical and personnel requirements that often cannot be achieved [4,5,6,7,8], in many areas of the Amazon region, far away from the main cities, where the population is widely dispersed and few health centres exist. Because of the reasons mentioned above and with the appearance of severe vivax malaria cases in different countries around the world in the last years [9], it is imperative to have a rapid and appropriate diagnosis method for malaria in Peru
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