Obare Method Calculator

The Obare Method Calculator is a tool to support researchers using microscopy in malaria research by calculating the mean parasite density and assessing whether two blood samples are concordant. It is a Microsoft Excel-based tool developed to facilitate adherence to the recommendations for internal quality control (IQC) defined in the recently released methods manual ‘Microscopy for the detection, identification and quantification of malaria parasites on stained thick and thin blood films in research settings’ (WHO 2015).


Publication Version
Publication Code
Publication Code Clinical

How it works

  • The operator must enter a unique ID for each slide from which data is entered for assessment
  • The Calculator allows the user to select:
  1. The film type (thick or thin) on which the malaria parasite density was assessed
  2. Parasite counts as total count, or separately for each species identified on the film (all detected species must be reported even in the latter case)
  3. Various methods for counting parasites: Thick film – parasites per microlitre, parasite and WBC counts, parasite and number of high poser fields (along with field number of the ocular lens and magnification of the objective lens); thin film – parasites per microlitre, parasite and RBC counts.
  • Data entered by the user are recorded on a separate sheet of the Excel file.

Although reasonable care has been taken while developing this calculator, it is recommended that users should test the calculator to ensure that it performs as they expect it to. If users find any errors or inconsistencies, please contact Mehul Dhorda – mehul.dhorda(at)wwarn.org. The developers cannot accept any liability for any loss of data, mis-reporting, or errors arising as a result of any reliance placed on this calculator.

This calculator may be copied, distributed, and generally re-used for non-commercial purposes provided such use includes the appropriate citation/reference: ‘Obare Method Calculator v.1.0 (2015). Matthew Rosen, Mehul Dhorda, David Bell, Michelle Gatton. www.wwarn.org'