Field evaluation of the diagnostic performance of EasyScan GO: a digital malaria microscopy device based on machine-learning

• Main Authors: Debashish Das, Ranitha Vongpromek, Thanawat Assawariyathipat, Ketsanee Srinamon, Kalynn Kennon, Kasia Stepniewska, Aniruddha Ghose, Abdullah Abu Sayeed, M. Abul Faiz, Rebeca Linhares Abreu Netto, Andre Siqueira, Serge R. Yerbanga, Jean Bosco Ouédraogo, James J. Callery, Thomas J. Peto, Rupam Tripura, Felix Koukouikila-Koussounda, Francine Ntoumi, John Michael Ong’echa, Bernhards Ogutu, Prakash Ghimire, Jutta Marfurt, Benedikt Ley, Amadou Seck, Magatte Ndiaye, Bhavani Moodley, Lisa Ming Sun, Laypaw Archasuksan, Stephane Proux, Sam L. Nsobya, Philip J. Rosenthal, Matthew P. Horning, Shawn K. McGuire, Courosh Mehanian, Stephen Burkot, Charles B. Delahunt, Christine Bachman, Ric N. Price, Arjen M. Dondorp, François Chappuis, Philippe J. Guérin, Mehul Dhorda
• Other Authors: Faculty of Tropical Medicine, Mahidol University
• Format: Article
• Published: 2022
• Subjects: Immunology and Microbiology; Medicine
• Online Access: https://repository.li.mahidol.ac.th/handle/123456789/74075
• Institution: Mahidol University

Background: Microscopic examination of Giemsa-stained blood films remains the reference standard for malaria parasite detection and quantification, but is undermined by difficulties in ensuring high-quality manual reading and inter-reader reliability. Automated parasite detection and quantification may address this issue. Methods: A multi-centre, observational study was conducted during 2018 and 2019 at 11 sites to assess the performance of the EasyScan Go, a microscopy device employing machine-learning-based image analysis. Sensitivity, specificity, accuracy of species detection and parasite density estimation were assessed with expert microscopy as the reference. Intra- and inter-device reliability of the device was also evaluated by comparing results from repeat reads on the same and two different devices. This study has been reported in accordance with the Standards for Reporting Diagnostic accuracy studies (STARD) checklist. Results: In total, 2250 Giemsa-stained blood films were prepared and read independently by expert microscopists and the EasyScan Go device. The diagnostic sensitivity of EasyScan Go was 91.1% (95% CI 88.9–92.7), and specificity 75.6% (95% CI 73.1–78.0). With good quality slides sensitivity was similar (89.1%, 95%CI 86.2–91.5), but specificity increased to 85.1% (95%CI 82.6–87.4). Sensitivity increased with parasitaemia rising from 57% at < 200 parasite/µL, to ≥ 90% at > 200–200,000 parasite/µL. Species were identified accurately in 93% of Plasmodium falciparum samples (kappa = 0.76, 95% CI 0.69–0.83), and in 92% of Plasmodium vivax samples (kappa = 0.73, 95% CI 0.66–0.80). Parasite density estimates by the EasyScan Go were within ± 25% of the microscopic reference counts in 23% of slides. Conclusions: The performance of the EasyScan Go in parasite detection and species identification accuracy fulfil WHO-TDR Research Malaria Microscopy competence level 2 criteria. In terms of parasite quantification and false positive rate, it meets the level 4 WHO-TDR Research Malaria Microscopy criteria. All performance parameters were significantly affected by slide quality. Further software improvement is required to improve sensitivity at low parasitaemia and parasite density estimations. Trial registration ClinicalTrials.gov number NCT03512678.