The role of infected red blood cells flag (InR) of Mindray BC 6800 plus in malaria diagnosis

An 8-year-old patient was admitted to the Pediatric Emergency Department of Novara's Hospital (Italy) with fever, headache, asthenia, inappetence, abdominal pain, and vomiting events following food intake. Complete blood count showed anemia (hemoglobin = 113 g/L; normal reference range: 115–135 g/L), thrombocytopenia (platelets = 111 × 109/L; normal reference range: 133–427 × 109/L), lymphocytopenia (lymphocytes = 1.14 × 109/L; normal reference range: 1.20–6.00 × 109/L), and an increase of inflammatory indices (C-Reactive Protein = 8.75 mg/dL; normal reference range: 0–1 mg/dL). In addition, the BC 6800 Plus (Mindray, Medical Systems; Shenzhen, China) indicated the presence of malaria-infected red blood cells (iRBCs). The WBC DIFF chart showed a clear clustering of Plasmodium-infected erythrocytes (Figure 1A), and the three-dimensional analysis technique (SF Cube) allowed a clearer representation of a subpopulation with a distinct and unique position in the scattergram (Figure 1B). The BC 6800 Plus was able to provide two special flags for malaria-infected red blood cells: “InR#” (= 0.80 × 109/L) corresponding to the number of malaria-infected red blood cells per 109/L and InR‰ (= 0.19‰), refers to number of infected RBCs per 1000 RBC. The patient's peripheral blood smear (SC −120 Mindray, Medical Systems) was analyzed using the automated digital cell morphology analyzer MC −80 (Mindray, Medical System), and the presence of intraerythrocytic inclusions (merozoites) was confirmed (Figure 2). Diagnostic testing was recommended to confirm the presence of malaria parasites. The rapid malaria test (Paramax-3, Effegiemme), which can detect malaria's antigen, showed negativity for P. vivax and P. falciparum but positivity for P. spp. In addition, the thin smear showed the presence of rare forms of P. spp. at the schizont stage with a parasitaemia index < of 0.1%. Surprisingly, the child had traveled to Nigeria 18 months earlier, suggesting possible infection with P. ovale or P. malariae. P. ovale has a dormant phase in the liver from which it emerges later and the incubation period varies from a few weeks to several months.1 In P. malariae, on the other hand, there is no relapse of persistent parasites in the liver stage, but parasites in the blood stage persist for an extremely long time, usually the life of the human host. Based on morphological characteristics, infected erythrocytes indicate P. malariae infection (Figure 2A–D). The host cells present a predominantly round shape characterized by RBCs not enlarged by the growth of the parasite but their size are comparable to healthy RBCs and James' Dots that characterized P. ovale infections were not present in the cytoplasm.2 The gametocytes of P. malariae are round to oval with scattered brown pigment and the schizonts have 6 to 12 merozoites with large nuclei grouped around a mass of coarse, dark brown pigment (hemozoin), that may occasionally be arranged as a rosette pattern (Figure 2A–D). The patient started therapy with Artesunato, parasitemia was monitored during treatment to confirm adequate response to therapy, and after 3 days the thin smear was negative for Plasmodium. This case demonstrates the utility of Mindray BC6800 Plus analyzer in malaria diagnosis, even in the presence of low percentages of parasitemia, suggests high sensitivity of the dedicated flags for iRBCs3 which should be confirmed by larger studies of larger numbers of cases. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.