Evaluation of an immunochromatography test for malaria diagnosis under different storage conditions

Abstract

COMUNICAÇÃO/COMMUNICATIONMalaria is endemic in the Brazilian Amazon region. Of the four known human malaria parasites, Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale, only the first three species have been detected in Brazil. The immense area of land and water, and the uncontrolled occupation of the Brazilian Amazon region, associated with the lack of personnel to carry out rapid diagnosis, all contribute to the elevated number of malaria cases in this region 2 . Rapid and accurate diagnosis of malaria is essential for reducing morbidity and mortality as well as for control purposes. Laboratory diagnosis of malaria has traditionally relied upon identification of the protozoan in peripheral blood using microscopic examination of thick and thin blood smears 10 . This procedure is labor-intensive, time consuming and dependent on training and expert knowledge, particularly for the interpretation of mixed infections and in cases with low parasitemias 1 4 .During the last few years, alternative immunochromatography tests (ICT) have been developed showing potential for enhancing speed and accuracy in the diagnosis of both falciparum and vivax malaria, particularly where diagnostic tests are not available, such as in rural and remote areas 8 . Newer ICTs make use of a second pan-malarial antibody, which is supposed to detect all four malarial species that infect humans. The OptiMal test (Flow, USA), which is currently marketed by DiaMed, Switzerland, detects a Plasmodium falciparum-specific lactate dehydrogenase (LDH) and a second-generation pLDH common to all human malaria parasites 3 . The purpose of the present study was to evaluate the diagnostic performance of the pLDH for diagnosis under various storage conditions. 195Penhalbel RSR et al A total of 111 positive (75 Plasmodium vivax, 34 Plasmodium falciparum and 2 Plasmodium malariae) and 40 negative samples analyzed by the thick blood smear method were also evaluated using the OptiMal test (according to manufacturer's instructions). The samples from P. vivax malaria patients showed parasite density between 250 and 5,500 infected red blood cells/mm 3 , while in P. falciparum samples the parasitemia ranged from 465 to 7,500 infected red blood cells/ mm 3 . Two samples of P. malariae showed parasite density below 50 infected red blood cells/mm 3 . The OptiMal-IT kits (DiaMed-ID AS) were stored at three different temperatures (25°C, 30°C and 39°C) for 24, 48 and 72 hours before use.The OptiMal-IT kit provided negative results in all 40 samples with no parasites in the microscopy examination (control group). The test could detect the positive samples that were seen in the microscopy examination at all evaluated temperatures and periods of storage. It was observed that the pink-line signals indicating positive results were constant under the same conditions. We could not detect either of the two P. malariae samples at any of the different temperatures and storage periods for the kits.Notable antigens for the diagnosis of malar...

Performance of an immuno-rapid malaria Pf/Pv rapid diagnostic test for malaria diagnosis in the Western Brazilian Amazon

“…Another study also carried out in the Amazon region, evaluated the OptiMal-IT®. This test showed good sensitivity in all the conditions studied, only failing in 2 samples of Plasmodium malariae 8 . Similarly, a study performed at a primary health care unit in Manaus, Amazonas comparing OptiMal-IT® and ICT-Pf/Pv® rapid tests showed sensitivities of 72% and 78% and specificities of 92% and 100%, respectively, compared to light microscopy 9 .…”