Potential application of the haematology analyser XN-31 prototype for field malaria surveillance in Kenya. 2022

Wataru Kagaya, and Ikki Takehara, and Kyoko Kurihara, and Michael Maina, and Chim W Chan, and Gordon Okomo, and James Kongere, and Jesse Gitaka, and Akira Kaneko
Department of Virology and Parasitology/Research Center for Infectious Disease Sciences, Graduate School of Medicine, Osaka Metropolitan University, 1-4-3, Asahimachi, Abeno-ku, Osaka, 545-8585, Japan.

BACKGROUND Simple and accurate diagnosis is a key component of malaria control programmes. Microscopy is the current gold standard, however it requires extensive training and the results largely rely on the skill of the microscopists. Malaria rapid diagnostic tests (RDT) can be performed with minimal training and offer timely diagnosis, but results are not quantitative. Moreover, some Plasmodium falciparum parasites have evolved and can no longer be detected by existing RDT. Developed by the Sysmex Corporation, the XN-31 prototype (XN-31p) is an automated haematology analyser capable of detecting Plasmodium-infected erythrocytes and providing species differentiation and stage specific parasite counts in venous blood samples without any preparation in approximately one minute. However, factors such as stable electricity supply in a temperature-controlled room, cost of the instrument and its initial set-up, and need for proprietary reagents limit the utility of the XN-31p across rural settings. To overcome some of these limitations, a hub and spoke diagnosis model was designed, in which peripheral health facilities were linked to a central hospital where detection of Plasmodium infections by the XN-31p would take place. To explore the feasibility of this concept, the applicability of capillary blood samples with the XN-31p was evaluated with respect to the effect of sample storage time and temperature on the stability of results. METHODS Paired capillary and venous blood samples were collected from 169 malaria-suspected outpatients in Homa Bay County Referral Hospital, Kenya. Malaria infections were diagnosed with the XN-31p, microscopy, RDT, and PCR. Capillary blood samples were remeasured on the XN-31p after 24 h of storage at either room (15-25 °C) or chilled temperatures (2-8 °C). RESULTS Identical results in malaria diagnosis were observed between venous and capillary blood samples processed immediately after collection with the XN-31p. Relative to PCR, the sensitivity and specificity of the XN-31p with capillary blood samples were 0.857 and 1.000, respectively. Short-term storage of capillary blood samples at chilled temperatures had no adverse impact on parasitaemia and complete blood counts (CBC) measured by the XN-31p. CONCLUSIONS These results demonstrate the potential of the XN-31p to improve routine malaria diagnosis across remote settings using a hub and spoke model.

UI MeSH Term Description Entries
D007630 Kenya A republic in eastern Africa, south of ETHIOPIA, west of SOMALIA with TANZANIA to its south, and coastline on the Indian Ocean. Its capital is Nairobi. Republic of Kenya
D008288 Malaria A protozoan disease caused in humans by four species of the PLASMODIUM genus: PLASMODIUM FALCIPARUM; PLASMODIUM VIVAX; PLASMODIUM OVALE; and PLASMODIUM MALARIAE; and transmitted by the bite of an infected female mosquito of the genus ANOPHELES. Malaria is endemic in parts of Asia, Africa, Central and South America, Oceania, and certain Caribbean islands. It is characterized by extreme exhaustion associated with paroxysms of high FEVER; SWEATING; shaking CHILLS; and ANEMIA. Malaria in ANIMALS is caused by other species of plasmodia. Marsh Fever,Plasmodium Infections,Remittent Fever,Infections, Plasmodium,Paludism,Fever, Marsh,Fever, Remittent,Infection, Plasmodium,Plasmodium Infection
D010963 Plasmodium falciparum A species of protozoa that is the causal agent of falciparum malaria (MALARIA, FALCIPARUM). It is most prevalent in the tropics and subtropics. Plasmodium falciparums,falciparums, Plasmodium
D003955 Diagnostic Tests, Routine Diagnostic procedures, such as laboratory tests and x-rays, routinely performed on all individuals or specified categories of individuals in a specified situation, e.g., patients being admitted to the hospital. These include routine tests administered to neonates. Admission Tests, Routine,Hospital Admission Tests,Physical Examination, Preadmission,Routine Diagnostic Tests,Admission Tests, Hospital,Diagnostic Test, Routine,Diagnostic Tests,Examination, Preadmission Physical,Preadmission Physical Examination,Routine Diagnostic Test,Test, Routine Diagnostic,Tests, Diagnostic,Tests, Hospital Admission,Tests, Routine Diagnostic,Admission Test, Hospital,Admission Test, Routine,Diagnostic Test,Examinations, Preadmission Physical,Hospital Admission Test,Physical Examinations, Preadmission,Preadmission Physical Examinations,Routine Admission Test,Routine Admission Tests,Test, Diagnostic,Test, Hospital Admission,Test, Routine Admission,Tests, Routine Admission
D006405 Hematology A subspecialty of internal medicine concerned with morphology, physiology, and pathology of the blood and blood-forming tissues.
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D012680 Sensitivity and Specificity Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed) Specificity,Sensitivity,Specificity and Sensitivity
D016778 Malaria, Falciparum Malaria caused by PLASMODIUM FALCIPARUM. This is the severest form of malaria and is associated with the highest levels of parasites in the blood. This disease is characterized by irregularly recurring febrile paroxysms that in extreme cases occur with acute cerebral, renal, or gastrointestinal manifestations. Plasmodium falciparum Malaria,Malaria, Plasmodium falciparum

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