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Towards malaria microscopy at the point-of-contact: an assessment of the diagnostic performance of the Newton Nm1 microscope in Uganda

Published online by Cambridge University Press:  04 August 2014

J. RUSSELL STOTHARD ,
BETTY NABATTE ,
JOSE C. SOUSA-FIGUEIREDO  and
NARCIS B. KABATEREINE
J. RUSSELL STOTHARD*
Affiliation:
Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
BETTY NABATTE
Affiliation:
Vector Control Division, Ministry of Health, P.O. Box 1661, Kampala, Uganda
JOSE C. SOUSA-FIGUEIREDO
Affiliation:
Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
NARCIS B. KABATEREINE
Affiliation:
Vector Control Division, Ministry of Health, P.O. Box 1661, Kampala, Uganda
*
*Corresponding author. Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK. E-mail: r.stothard@liverpool.ac.uk
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Summary

Malaria microscopy in sub-Saharan Africa is often restricted by access to light microscopes. To address this gap, a novel portable inverted monocular microscope, the Newton Nm1, was designed and is now commercially available. Its diagnostic performance was assessed in a blinded-slide trial at ×1000 (oil) of Giemsa-stained thick blood films against a conventional microscope as undertaken by four Ugandan Ministry of Health technicians. With the Newton Nm1, diagnostic performance was: sensitivity 93·5% (95% confidence interval (CI) 78·6–99·2%), specificity 100·0% (95% CI 82·4–100·0%), positive predictive value 100·0% (95% CI 88·1–100·0%) and negative predictive value 90·5% (95% CI 69·6–98·8%). Discordance was due to a systematic error underestimating parasitaemia by ~45%; when counting Plasmodium parasites against 200 white blood cells, blood films with low parasitaemia (i.e. <100 μL−1 of blood) could be overlooked and misclassified. By contrast, specificity was excellent with no false positives encountered. Whilst proven useful, especially in resource-poor environments, it is still unclear how we can ensure the uptake of the Newton Nm1 within sub-Saharan Africa.

Keywords

McArthur microscopemalariadiagnosismicroscopyBland-Altmanevaluation
Type
Special Issue Article
Information
Parasitology , Volume 141 , Issue 14: Symposia of the British Society for Parasitology Volume 52 Advances in diagnostics for parasitic diseases , December 2014 , pp. 1819 - 1825
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Copyright
Copyright © Cambridge University Press 2014 

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