The tests are based on the detection of the Histidine Rich Protein 2 (HRP2) which is a glycoprotein specific to Plasmodium falciparum exposed on the surface of the infected red blood cell, and at the same time, actively secreted by the intracellular parasites. 

Its secretion is constant throughout the erythrocytic cycle of the parasite with a peak at the moment of the rupture of the schizonts.

The HRP2 was isolated on strains of Plasmodium falciparum from Africa, Asia and South America.

This set of criteria led to the choice of the HRP2 as a marker of infection by Plasmodium falciparum. 

The sensitivity and specificity of these tests, a very high positive predictive value, good stability in the field and the absence of crossed reaction with the other plasmodium species of human interest helped bring these tests into the everyday domain. 

They are presented in unitary form. Performance and reading require no equipment.  The  HRP2 is detected in a sample of whole  blood through the addition of a monoclonal anti-HRP2 anti-body coupled to a colored developer.   

The ParaSight®-F test 

The ParaSight®-F test (Becton Dickinson Tropical Diseases Diagnostics, Sparks, MD, USA) is a manual test on a strip. It requires the successive use of 3 reagents. It shows the required qualities of thermo-resistance for use in the field: 9 months at ambient temperature and 6 months at 37°C. 

The MalaQuick®test 

The MalaQuick® test (ICT Diagnostics, Sydney, Australia, distributed in France by the Laboratoires Fumouze) has the advantage of being simple to use. It is packed in kits of 2, 3, 5 and 25 tests and only uses a single liquid reagent. The tests are presented in folding card form which means that they may be kept with the possibility of deferred reading which limits the risk of contact of the manipulator with the patient’s blood. The manufacturer recommends that they be kept in a positive cold, but studies in tropical areas comparing the results of kits kept at ambient temperature and in positive cold have not shown any discordance. Thus, this test may be recommended as much in a precarious situation as in hospital practice.

These tests are especially useful as they may address medical and paramedical personnel insufficiently trained in direct parasitological diagnosis.

In malaria endemic areas, the detection of HRP2 would seem to respond to the technical criteria of the WHO characterizing a diagnostic test of Plasmodium falciparum adapted to the peripheral healthcare structures which have no access to a microscope.

For the diagnosis of imported malaria, this test cannot replace the microscopic techniques due to its strict species specificity and its absence of quantification. But it can be used in association with them, for its great sensitivity and its low detection threshold make it a very useful ad hoc test for low level parasitemia, especially in the event of prior self medication.  

They present several advantages:

• easy performance by staff non-trained in parasitological techniques 
• incontestable interpretation in most cases 
• specific test for Plasmodium falciparum, with its therapeutic and operational implications that may lead to a positive result 
• feasibility in the field.   

They should not be used alone, except in conditions of isolation, for they do not provide all the elements necessary for the optimal therapeutic care of febrile crises in endemic malarial areas:

• specificity of Plasmodium falciparum ("multi-species" tests exist, but are not yet marketed in France) 
• detection of trophozoite forms only
• absence of correlation between the intensity of the signal and parasitic density.