Muehlenbachs et al developed a grading scheme for histologic changes in the placenta associated with malaria. Placental involvement has a number of implications for the outcome of a gestation. The authors are from the University of Washington in Seattle, National Institute of Allergy and Infectious Diseases, Shoklo Malaria Research Institute, Mahidol Oxford University Tropical Medicine Research Program, Natational Insittue of Medical Research in Tanzania and Churchill Hospital (Oxford).
Examination: histologic sections of a placenta stained with a Giemsa stain
Malaria pigment score:
(1) based on examination of >= 60 microscopic fields using a 60x objective
(1) pigment in inflammatory cells is not counted
(2) fields consisting of deciduas, basal plate, stem villi are not counted
(3) looking for any malaria pigment deposited in fibrin in an intervillous space
Parameters:
(1) level of intervillous inflammation
(2) malaria pigment score
Intervillous Inflammation
Grade
none or minimal
I
present (intermediate)
II
massive (sheets of densely packed mononuclear cells)
III
malaria pigment count =
= (microscopic fields with malaria pigment in fibrin) / (number of valid microscopic fields counted) * 100%
Malaria Pigment Score
Grade
<= 10%
I
10.1 to 40%
II
> 40%
III
Interpretation:
• High grades for inflammation and pigment correlate with fetal growth retardation and miscarriage.
• The histologic grades also correlated with levels of the chemokine CXCL13.
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