Field evaluation of a rapid diagnostic test (Parascreen™) for malaria diagnosis in the Peruvian Amazon

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.

Study on validity of a rapid diagnostic test kit versus light microscopy for malaria diagnosis in Ahmedabad city, India

“…The sensitivity of RDT for the diagnosis of malaria in the present study was 98.8% and the specificity was 91.5%. These figures were similar to those found in several other studies [8,[10][11][12][13], although in one study the sensitivity and specificity of RDTs compared with microscopy results were 85.3% and 59.8% respectively [7].…”

“…In Gujarat State, 71 480 malaria cases were reported during 2012, 13.4% of these due to Plasmodium falciparum [2]. In Ahmedabad, the largest city in Gujarat, the total number of malaria cases was 18 802, with 15.4% being P. falciparum cases.…”

Situação da malária na tríplice fronteira entre Brasil, Colômbia e Peru

“…A pesar das limitações técnicas de alguns dos TDR comerciais, esse será um processo importante para a melhoria do diagnóstico, especialmente nas áreas afastadas, de difícil acesso e sem energia elétrica para a realização de diagnóstico microscópico 17 . De qualquer forma, sugere-se a implementação de pesquisas para melhor avaliar o uso dos TDR nessa região da Amazônia.…”

Low sensitivity of malaria rapid diagnostic tests stored at room temperature in the Brazilian Amazon Region

“…Although exposure to high temperatures can explain the low sensitivity of the ICT-Now Pf/Pan test for the detection of P. falciparum [10], other factors must also be considered. For example, the absence of the target antigen in the parasite due to polymorphism or deletion of the gene that codes for HRP2 found in strains isolated in several malaria endemic regions is a possibility [23,25,26]. However, the occurrence of these polymorphisms was described in just one strain of P. falciparum isolated in Brazil [27].…”

“…In most of the studies performed in endemic regions the tests were kept under ideal storage conditions [5,15,17,25]. In this study, the intentional exposure of the RDT to a wider temperature range (20.2°C to 34.4°C) for a prolonged period of time can be considered the main factor responsible for the low sensitivity observed.…”