Comparison of immuno-fluorescence microscopy and optical microscopy after Giemsa staining in the diagnosis of malaria during pregnancy in Buea, Cameroon

Abstract

Malaria in pregnancy remains a significant threat in sub-Saharan Africa as it is associated with suboptimal pregnancy outcomes. Due to the fact that the current standard diagnostic method is cumbersome, we assessed the diagnostic performance of an alternate method-fluorescent microscopy, compared to optical microscopy after Giemsa staining- the current standard.Venous blood samples were collected from 407 consenting pregnant women and tested by optical microscopy (OM) after Giemsa staining and by fluorescent microscopy (FM) using the Partec-Cyscope (Partec GmbH, Munster, Germany). All participants were asymptomatic at the time of enrollment. Of the 407 samples tested by OM, 255 (62.5%) were plasmodiumpositive. Of the 255 OM positive samples, 207 were also plasmodium-positive by FM, thus a sensitivity of 81.1% (95% confidence interval (CI): 75.8, 85.8%). Of the 152 samples negative by OM, 75 were also negative by FM, thus a specificity of 49.3% (95%CI: 41.1, 57.6%). The positive and negative predictive values of FM were respectively 72.9% (95%CI: 67.3, 78.0%) and 61.0% (95%CI: 51.8, 69.6%). The percentage agreement between both methods was 69.3% (Kappa=0.32,  p-value<0.01). There was moderate agreement between FM and OM results. The low specificity and negative predictive value of FM suggest a high likelihood of false negative results if FM is used in place of OM. OM after Giemsa staining remains the gold standard.

Keywords: Diagnostic performance, sensitivity, specificity, positive predictive value, negative predictive value, Cameroon.