How to report malaria microscopy results

Reporting proper malaria microscopy results is important in managing malaria-infected patients and provides reliable data for intervention programs.

Reporting requirements

• Light Microscope
• Stained slides – with a specimen for investigation.
• Lab register
• Patient result forms

Basic Malaria microscopy slide examination

1. Examine a stained slide under a light microscope.
2. Count and record all malaria species and stages seen.
3. Count the number of white blood cells relative to parasites seen.
4. Calculate the white blood cell count of the patient. If not possible, use an approximate white blood cell count of 8000 cells/uL.
5. Calculate parasitic count (parasites per micro-liter of blood):

(No. of asexual parasites counted * WBC count)/ No. of white cells relative to parasites

How to report malaria microscopy results

1. Plasmodium falciparum trophozoites = 200, white blood cells relative to parasites = 220, estimated white blood cell count = 8000 WBC/uL, Parasitic count = (200*8000)/220. Report as: Plasmodium falciparum trophozoites =7273 parasites/uL of blood.
2. Plasmodium vivax trophozoites= 90, white blood cells relative to parasites = 600, white blood cell count = 7000, Parasitic count = (90*7000)/600. Report as Plasmodium vivax trophozoites =1050 parasites/uL of blood. NOTE, in mixed infections, count all the species together (sexual and asexual stages) as shown in the next example.
3. Plasmodium vivax trophozoites = 200, Plasmodium falciparum gametocytes = 130, No of parasites = 200+130 which is 330(all stages), white blood cells relative to parasites = 300, estimated white blood cell count = 8000 WBC/uL, Parasitic count = (330*8000)/300. Report as: Plasmodium vivax trophozoites and Plasmodium falciparum gametocytes =8800 parasites/uL of blood.

Also, report:

1. Report Schizonts as they might indicate disease severity.
2. Gametocytes. Count gametocytes of Plasmodium falciparum separately but still include them in the total parasitic count. Gametocyte count for Plasmodium malariae or Plasmodium vivax is not required since it is difficult to separate them from asexual parasites.

Report ‘No malaria parasites seen’, rather than ‘Negative’.

Avoid the “plus +” system as it provides a wrong estimate of malaria parasites.

Reference: WHO SOP: MM-SOP-06b-eng