Systematic comparison of two methods to measure parasite density from malaria blood smears (original) (raw)

Abstract

This study was designed to directly compare the accuracy, reproducibility, and efficiency of three methods commonly used to measure blood-stage malaria parasite density from Giemsa-stained blood films. Parasites and white blood cells (WBCs) were counted in 154 thick films by two independent microscopists. Forty-six slides were read by counting parasitized red blood cells (RBCs) in the thin film. Using these same slides, parasites were again counted by two independent microscopists using an ocular grid. Overall, parasite densities were significantly lower and discrepancy between readers was higher when using the grid method compared to the WBC method, but there was no difference when compared to the RBC method. When one reader who had difficulty with the grid method was excluded, the discrepancy between readers was equivalent for the three methods. Densities and discrepancy between readers were indistinguishable when parasites were counted until 200 or 500 WBCs. Counting beyond 200 WBCs may not significantly improve parasite density measurements. Using an ocular grid directly measures parasites per volume rather than using a WBC per microliter conversion factor and eliminates the need to switch from the thick film to the thin film for high parasitemias. However, significant differences in densities measured by the grid method and the WBC method need to be evaluated.

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Acknowledgement

All experiments comply with the laws of the country where they were performed.

Author information

Authors and Affiliations

1. Fogarty International Center, NIH, Bethesda, MD, USA
   Wendy Prudhomme O’Meara & F. Ellis McKenzie
2. Malaria Micrsocopy Center for Excellence, Walter Reed Project, United States Army Medical Research Unit–Kenya, Center for Clinical Research, Kenya Medical Research Institute, Kisumu, Kenya
   Shon Remich, Bernhards Ogutu, Ramadan Mtalib, Peter Obare, Frederick Oloo, Caroline Onoka & Joseph Osoga
3. Centers for Disease Control, Kenya Medical Research Institute, Kisumu, Kenya
   Martin Lucas
4. Walter Reed Army Institute of Research, Silver Spring, MD, USA
   Colin Ohrt

Authors

1. Wendy Prudhomme O’Meara
2. Shon Remich
3. Bernhards Ogutu
4. Martin Lucas
5. Ramadan Mtalib
6. Peter Obare
7. Frederick Oloo
8. Caroline Onoka
9. Joseph Osoga
10. Colin Ohrt
11. F. Ellis McKenzie

Corresponding author

Correspondence toWendy Prudhomme O’Meara.

Additional information

The opinions or assertions contained herein are the private views of the author, and are not to be construed as official, or as reflecting true views of the Department of the Army or the Department of Defense

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Prudhomme O’Meara, W., Remich, S., Ogutu, B. et al. Systematic comparison of two methods to measure parasite density from malaria blood smears.Parasitol Res 99, 500–504 (2006). https://doi.org/10.1007/s00436-006-0135-x

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• Received: 02 December 2005
• Accepted: 19 January 2006
• Published: 30 March 2006
• Issue date: September 2006
• DOI: https://doi.org/10.1007/s00436-006-0135-x

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