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<p>Abstract</p> <p>Background</p> <p>The 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 <it>Plasmodium falciparum </it>and lactate deshydrogenase from all <it>Plasmodium </it>species.</p> <p>Methods</p> <p>Parascreen™ 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-).</p> <p>Results</p> <p>332 patients with suspected non-complicated malaria who attended to the MOH health centres were enrolled between October and December 2006. For <it>P. falciparum </it>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-<it>P. falciparum </it>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 <it>P. falciparum </it>malaria, Se: 81.8%, Sp: 99.1%, PV+: 75%, PV-: 99.4, LR+: 87.27 and LR-: 0.18; and for non-<it>P. falciparum </it>malaria Se: 76.1%, Sp: 99.2%, PV+: 97.1%, PV-: 92.0%, LR+: 92.51 and LR-: 0.24.</p> <p>Conclusions</p> <p>The 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 <it>Plasmodium </it>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 <it>P. falciparum </it>malaria parasites lacking <it>pfhrp2 </it>gene in this region.</p>