The effect of monthly sulfadoxine-pyrimethamine, alone or with azithromycin, on PCR-diagnosed malaria at delivery: a randomized controlled trial.

BACKGROUND: New regimens for intermittent preventive treatment in pregnancy (IPTp) against malaria are needed as the effectiveness of the standard two-dose sulfadoxine-pyrimethamine (SP) regimen is under threat. Previous trials have shown that IPTp with monthly SP benefits HIV-positive primi- and secundigravidae, but there is no conclusive evidence of the possible benefits of this regimen to HIV-negative women, or to a population comprising of both HIV-positive and -negative women of different gravidities. METHODS: This study analyzed 484 samples collected at delivery as part of a randomized, partially placebo controlled clinical trial, conducted in rural Malawi between 2003 and 2007. The study included pregnant women regardless of their gravidity or HIV-infection status. The participants received SP twice (controls), monthly SP, or monthly SP and two doses of azithromycin (AZI-SP). The main outcome was the prevalence of peripheral Plasmodium falciparum malaria at delivery diagnosed with a real-time polymerase chain reaction (PCR) assay. FINDINGS: Overall prevalence of PCR-diagnosed peripheral P. falciparum malaria at delivery was 10.5%. Compared with the controls, participants in the monthly SP group had a risk ratio (95% CI) of 0.33 (0.17 to 0.64, P<0.001) and those in the AZI-SP group 0.23 (0.11 to 0.48, P<0.001) for malaria at delivery. When only HIV-negative participants were analyzed, the corresponding figures were 0.26 (0.12 to 0.57, P<0.001) for women in the monthly SP group, and 0.24 (0.11 to 0.53, P<0.001) for those in the AZI-SP group. CONCLUSIONS: Our results suggest that increasing the frequency of SP administration during pregnancy improves the efficacy against malaria at delivery among HIV-negative women, as well as a population consisting of both HIV-positive and -negative pregnant women of all gravidities, in a setting of relatively low but holoendemic malaria transmission, frequent use of bed nets and high SP resistance.

Comparison of real-time PCR and microscopy for malaria parasite detection in Malawian pregnant women.

BACKGROUND: New diagnostic tools for malaria are required owing to the changing epidemiology of malaria, particularly among pregnant women in sub-Saharan Africa. Real-time PCR assays targeting Plasmodium falciparum lactate dehydrogenase (pfldh) gene may facilitate the identification of a high proportion of pregnant women with a P. falciparum parasitaemia below the threshold of microscopy. These molecular methods will enable further studies on the effects of these submicroscopic infections on maternal health and birth outcomes. METHODS: The pfldh real-time PCR assay and conventional microscopy were compared for the detection of P. falciparum from dried blood spots and blood smears collected from the peripheral blood of 475 Malawian women at delivery. A cycle threshold (Ct) of the real-time PCR was determined optimizing the sensitivity and specificity of the pfldh PCR assay compared to microscopy. A real-time PCR species-specific assay was applied to identify the contribution to malaria infections of three Plasmodium species (P. falciparum P. ovale and P. malariae) in 44 discordant smear and pfldh PCR assay results. RESULTS: Of the 475 women, P. falciparum was detected in 11 (2.3%) by microscopy and in 51 (10.7%) by real-time PCR; compared to microscopy, the sensitivity of real-time PCR was 90.9% and the specificity 91.2%. If a Ct value of 38 was used as a cut-off, specificity improved to 94.6% with no change in sensitivity. The real-time PCR species-specific assay detected P. falciparum alone in all but four samples: two samples were mixed infections with P. falciparum and P. malariae, one was a pure P. malariae infection and one was a pfldh PCR assay-positive/species-specific assay-negative sample. Of three P. malariae infections detected by microscopy, only one was confirmed by the species-specific assay. CONCLUSIONS: Although microscopy remains the most appropriate method for clinical malaria diagnosis in field settings, molecular diagnostics such as real-time PCR offer a more reliable means to detect malaria parasites, particularly at low levels. Determination of the possible contribution of these submicroscopic infections to poor birth outcomes and maternal health is critical. For future studies to investigate these effects, this pfldh real-time PCR assay offers a reliable detection method.