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Overview :
An approximate number of malaria parasite forms in the
peripheral blood can be estimated by counting the number of parasites for a
given number of white blood cells.
malaria count in the peripheral blood =
= (((number of parasites counted) / (number of white cells
counted)) * (WBC count))
where:
• The number of
white cells counted varies with the parasite load. At high levels of
parasitemia, 50 WBCs is sufficient. At low levels of parasitemia, larger
numbers of white blood cells should be counted to get meaningful results.
• WBC count is the
white blood cell count per microliter. The number of white cells to count can
vary depending if neutropenia or neutrophilia is present.
Interpretation:
• The count
derived is used initially as a rough estimate of parasite load, but is used
primarily to assess the effectiveness of therapy.
• The counts
should drop to 0 with effective therapy.
• Fulminant
disease will show rising levels of organisms.
• Organisms
showing drug resistance to current regimen should show no or minimal changes in
numbers.
Limitations: In
Plasmodium vivax infections parasites may be cleared from the blood yet the
patient have disease relapse unless "radical cure" of intrahepatic
forms is achieved.
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