Malaria rapid diagnostic tests in travel medicine

Abstract

Malaria is a serious condition in the non-immune traveller, and prognosis depends on timely diagnosis. Although microscopy remains the cornerstone of diagnosis, malaria rapid diagnostic tests (RDTs) are increasingly used in non-endemic settings. They are easy to use, provide results rapidly and require no specific training and equipment. Reported sensitivities vary between different RDT products but are generally good for Plasmodium falciparum, with RDTs detecting the P. falciparum antigen histidine-rich protein-2 (PfHRP2) scoring slightly better than P. falciparum-lactate dehydrogenase (Pf-pLDH)-detecting RDTs. Sensitivity is lower for Plasmodium vivax (66.0 - 88.0%) and poor for Plasmodium ovale (5.5 - 86.7%) and Plasmodium malariae (21.4 - 45.2%). Rapid diagnostic tests have several other limitations, including persistence of the PfHRP2 antigen, cross-reactions of P. falciparum with the non-falciparum test line and vice versa and (rare) false-positive reactions due to other infectious agents or immunological factors. False-negative results occur in the case of low parasite densities, prozone effect or pfhrp2 gene deletions. In addition, errors in interpretation occur, partly due to inadequacies in the instructions for use. Finally, RDTs do not give information about parasite density. In the diagnostic laboratory, RDTs are a valuable adjunct to (but not a replacement for) microscopy for the diagnosis of malaria in the returned traveller.In malaria endemic settings, special groups of travellers (those travelling for long periods, expatriates and short-stay frequent travellers) who are remote from qualified medical services may benefit from self-diagnosis by RDTs, provided they use correctly stored RDT products of proven accuracy, with comprehensive instructions for use and appropriate hands-on training.

Prozone-like phenomenon in travellers with fatal malaria: report of two cases

“…The latter detects parasitespecific antigens or enzymes and some have a certain ability to differentiate species, being powerful tools to achieve a quick diagnosis both in endemic and nonendemic regions. However, RDTs have limitations: quantification of parasitaemia is impossible, there is a possibility of technical and procedural errors, HRP2-based tests may remain positive for several weeks after malaria treatment alongside with false negative results occurrence [1]. These false negative results can occur both for very low and high parasite densities.…”

“…Other available RDTs target different P. falciparum antigen, namely Pf LDH and for those tests the prozone effect was not described. However, RDTs targeting HRP-2 have some advantages over those targeting Pf LDH, like higher sensitivity and higher heat resistance [1]. Probably RDTs combining both antigens can eliminate the shortcomings presented by each other, when used alone.…”

“…Malaria diagnosis in non-endemic countries remains a concern with approximately 10,000 cases of imported malaria occurring each year in European countries [1]. Timely diagnosis and treatment are crucial to tackle the potentially devastating effects of the disease.…”

“…Timely diagnosis and treatment are crucial to tackle the potentially devastating effects of the disease. Diagnosis of malaria by light microscopy examination of thin and thick blood films is still the gold standard [1], but rapid diagnostic tests (RDTs) are increasingly used both in non-endemic and endemic regions. These tests detect Plasmodium antigens in blood by antigen-antibody interaction on a nitrocellulose test strip and can target antigens specific of P. falciparum like the histidine-rich protein 2 (HRP-2) and lactate dehydrogenase (Pf-pLDH) or parasite antigens considered pan-specific (pLDH and aldolase).…”

Perioperative considerations of the patient with malaria

“…Nevertheless, these rapid diagnostic tests do not quantify the level of parasitemia, which is necessary in guiding appropriate treatment and response. 21 Once malaria is diagnosed, it is important to assess disease severity in order to initiate the appropriate treatment. This is generally based on species subtype, percentage of parasitized erythrocytes, and the degree of organ impairment.…”