Clinical practice: the diagnosis of imported malaria in children

The present paper reviews the diagnosis of imported malaria in children. Malaria is caused by a parasite called Plasmodium and occurs in over 100 countries worldwide. Children account for 10-15% of all patients with imported malaria and are at risk to develop severe and life-threatening complications especially when infected with Plasmodium falciparum. Case-fatality ratios vary between 0.2% and 0.4%. Children visiting friends and relatives in malaria endemic areas and immigrants and refugees account for the vast majority of cases. Symptoms are non-specific and delayed infections (more than 3 months after return from an endemic country) may occur. Microscopic analysis of the thick blood film is the cornerstone of laboratory diagnosis. For pragmatic reasons, EDTA-anticoagulated blood is accepted, provided that slides are prepared within 1 h after collection. Information about the Plasmodium species (in particular P. falciparum versus the non-falciparum species) and the parasite density is essential for patient management. Molecular methods in reference settings are an adjunct for species differentiation. Signals generated by automated hematology analyzers may trigger the diagnosis of malaria in non-suspected cases. Malaria rapid diagnostic tests are reliable in the diagnosis of P. falciparum but not for the detection of the non-falciparum species. They do not provide information about parasite density and should be used as an adjunct (and not a substitute) to microscopy. In case of persistent suspicion and negative microscopy results, repeat testing every 8-12 h for at least three consecutive samplings is recommended. A high index of suspicion and a close interaction with the laboratory may assure timely diagnosis of imported malaria.