What is the burden of submicroscopic malaria in pregnancy in central India?

Abstract

Background: Conventional microscopy underestimates the burden of malarial infection when compared with molecular diagnosis using polymerase chain reaction (PCR)-based methods. Lower density parasitemias serve as a reservoir for infection. We evaluated the prevalence of submicroscopic infections in an area of unstable malarial transmission in India and determined whether these infections negatively impacted maternal or fetal outcomes. Methods: This cross-sectional study (2007)(2008) was undertaken in two districts of Chhattisgarh, recruiting women from both antenatal clinics (ANCs) and delivery units (DUs). For ANC/DU subjects, peripheral/ placental blood, respectively, was obtained for conventional microscopy and collected onto filter paper for PCR analysis. Results: There were 3425 pregnant women, including 2477 ANC subjects and 948 DU subjects who had both microscopic and PCR samples available. Polymerase chain reaction detected significantly more Plasmodium infections than traditional light microscopy both from peripheral (3.4 vs 1.2%; OR 2.9, 95% confidence intervals (CIs) 1.9-4.5) and placental (4.2 vs 1.7%; OR 2.5, 95% CIs 1.4-4.8) blood samples. Submicroscopic infections were not associated with anemia or severe maternal anemia among ANC or DU participants and were not associated with low birth weight (LBW) among DU participants. In contrast, microscopically detected infections were associated with severe anemia and LBW. Conclusions: In this area of unstable malarial transmission from India, submicroscopic infections did not identify a set of pregnant women at increased risk for anemia or LBW. Until PCR techniques become much less expensive and available as a point of care test for the field setting, its use will be limited for malarial detection.

The Performance of a Rapid Diagnostic Test in Detecting Malaria Infection in Pregnant Women and the Impact of Missed Infections

“…Whether infections that are PCR positive but RDT or microscopy negative are associated with a poor outcome of pregnancy is less certain and is an important issue if ISTp is to be considered for implementation in some epidemiological situations. Some studies have shown an association between submicroscopic infections and maternal anemia [ 22 – 24 ] or low birth weight [ 25 , 26 ], but other studies have not shown any association between PCR positive but RDT or microscopy negative infections and an adverse outcome of pregnancy [ 27 , 28 ] as in our study. The reasons for this discrepancy is uncertain but it may reflect differences in the characteristics of the study population, the number of subjects studied, and the sensitivity of the RDT and PCR assays used.…”

Clinical Outcomes of Submicroscopic Infections and Correlates of Protection of VAR2CSA Antibodies in a Longitudinal Study of Pregnant Women in Colombia

“…However, only a few studies have examined the effects of SMIs in regions where P. falciparum and P. vivax cocirculate. P. falciparum and P. vivax SMIs at delivery were associated with poor outcomes in one study from Papua New Guinea (PNG) (27) but not in studies conducted in Colombia and India (10,28). In a multicenter study of pregnant women in Colombia, Guatemala, Brazil, India, and PNG, submicroscopic P. falciparum and P. vivax infections were not associated with either maternal anemia or LBW (29).…”

Impact of Submicroscopic Plasmodium falciparum Parasitaemia on Maternal Anaemia and Low Birth Weight in Blue Nile State, Sudan

“…The placenta provides an ideal environment for the sequestration of parasite-infected red blood cells that adhere to the adhesion molecule Chondroitin sulfate A (CSA) receptors in the placental syncytiotrophoblast with the parasite ligand VAR2CSA [5, 6]. Molecular detection methods of Plasmodium , particularly the polymerase chain reaction (PCR) method, have been shown to be significantly more sensitive in detecting low-level parasitaemia than the standard diagnostic method of thick blood film microscopy in both peripheral blood and placental blood [7–9].…”