Evaluation of the Diagnostic Capacity of Malaria by XN-31 Automate at Cotonou in an Endemic Area of Benin, West Africa

Reliable and rapid pre-force diagnosis of malaria is necessary in the fight against malaria. Due to the limitations of the Giemsa-stained thick and thin blood smears technique, new techniques are established for malaria diagnosis; this is the case with the XN-31 automated system. This study evaluates the performance of the XN-31 automated malaria diagnostic system compared to the Giemsa-stained thick and thin blood smears technique. 260 blood samples from plasma parasite positive individuals were collected between July 2021 and February 2022 at the Boni Clinic, along with the clinical information for each of these samples. These samples were run on the XN-31 automated system, which uses fluorescence flow cytometry to detect and quantify red blood cells parasitized by Plasmodium parasites and provides a complete blood count and visual image scattergram of the parasitized red blood cells for diagnosis of the species involved. The results from the automated system are compared with those obtained by reading the Giemsa-stained thick and thin blood smear slides, which are considered the reference method. Apart from one case of P. vivax only detected by the XN-31, both techniques mentioned the presence of P. falciparum (majority species), P. malariae and P. ovale in approximate proportions. In this study, the detection limit of the automaton is 40 parasites per ul of blood. A few cases of false positive, false negative and indeterminate were recorded by the machine. There was a strong correlation (r = 0.8019) between the Giemsa-stained thick and thin blood smears technique and the XN-31 machine in the estimation of parasite densities. The XN-31 can be used for clinical diagnosis of malaria in endemic areas. In case of diagnostic difficulties (undetermined, absence of scattergram) or abnormalities of red blood cells, it is necessary to dilute the sample to 1/7 or to use blood smears for the diagnosis of the species and the parasite load.