Comparison of real-time PCR and microscopy for malaria parasite detection in Malawian pregnant women
Open accessAbstract
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.
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Most malaria prevalence estimates by microscopy in pregnant women would probably be higher if more sensitive methods like PCR or placental histology were used.
“Most of the prevalence estimates were done by microscopy and they would probably be higher if more sensitive methods like PCR12 or placental histology13 were used.”
From Malaria in pregnancy. (2013) · cites this paper as [12]
Whether applied to peripheral blood or placental blood samples, PCR methods yield positivity rates 20% or more above those of blood smear microscopy.
“Whether applied to peripheral blood or placental blood samples, PCR methods yield positivity rates 20% or more above those of BS microscopy (Tables 3 & 4) [10,14–16,38–46].”
From Diagnosing malaria in pregnancy: An update (2012) · cites this paper as [42]
Other studies did not observe an association between submicroscopic infection and increased low birthweight.
“However, other studies did not observe an association between submicroscopic infection and increased LBW [15,42].”
From Diagnosing malaria in pregnancy: An update (2012) · cites this paper as [42]
The authors and others did not find an association between submicroscopic parasitemia and reduced birthweight.
“We and others ([42] and Figure 2) did not find an association between sub microscopic parasitemia and reduced birthweight, unlike parasitemia detected by either peripheral or placental BS, which is associated with a significant reduction in birthweight.”
From Diagnosing malaria in pregnancy: An update (2012) · cites this paper as [42]
The epidemiological characteristics and the consequences associated with submicroscopic plasmodial infection in pregnant women have been poorly evaluated.
“However, the epidemiological characteristics and the consequences associated with submicroscopic plasmodial infection in pregnant women have been poorly evaluated [19,20].”
From Submicroscopic infection of placenta by Plasmodium produces Th1/Th2 cytokine imbalance, inflammation and hypoxia in women from north-west Colombia (2014) · cites this paper as [20]
Data are conflicting about the impact of submicroscopic infections on LBW; some studies suggest increased risk and others no association.
“Similarly, the data are conflicting about the impact of submicroscopic infections on LBW; some studies suggest an increased risk 16,24 in the setting of submicroscopic infections and others no association. 20-23”
From What is the burden of submicroscopic malaria in pregnancy in central India? (2015) · cites this paper as [22]
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References 33 · Cited by 110
- Authors
- Rantala, A.-M., Taylor, S. M., Trottman, P. A., Luntamo, M., Mbewe, B., Maleta, K., Kulmala, T., Ashorn, P., & Meshnick, S. R.
- Affiliations
- Tampere University (FI)
- University of North Carolina at Chapel Hill (US)
- University of Malawi (MW)
- Corresponding author
- Meshnick, Steven R
- Venue
- Malaria Journal
- Published
- 2010-10-06
- Volume
- 9
- Issue
- 1
- Pages
- 269-269
- ISSN
- 1475-2875 (ISSN-L)
- PMC
- PMC2984567
- OpenAlex
- W2137454952
- Cited by
- 110
- References
- 33
- Citations by year
- 2026: 3 · 2025: 1 · 2024: 4 · 2023: 5 · 2022: 1 · 2021: 5 · 2020: 6 · 2019: 8 · 2018: 7 · 2017: 10 · 2016: 9 · 2015: 11 · 2014: 15 · 2013: 7 · 2012: 11
- FWCI
- 7.92
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- cc-by
- Locations
- Malaria Journal (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- Tampere University Institutional Repository (Tampere University) (publishedVersion)
- Tampere University Institutional Repository (Tampere University) (submittedVersion)
- Carolina Digital Repository (University of North Carolina at Chapel Hill) (submittedVersion, cc-by)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
- Greater South Information System
- Funders
- Pirkanmaan Sairaanhoitopiiri
- National Institute of Allergy and Infectious Diseases (R21 AI016785)
- Topics
- Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Malaria Research and Control
- Health Sciences › Medicine › Genetics › Hemoglobinopathies and Related Disorders
- Life Sciences › Immunology and Microbiology › Parasitology › Bird parasitology and diseases
- Keywords
- malaria parasite detection, Plasmodium falciparum, microscopy, submicroscopic malaria infection, pregnant women, dried blood spots, Plasmodium malariae, Plasmodium ovale, mixed malaria infection, species-specific PCR assay, sensitivity and specificity, Malawi
- MeSH terms
- Adolescent, Adult, Africa, Blood, Desiccation, Female, Humans, Infant, Newborn, L-Lactate Dehydrogenase, Malaria, Malawi, Microscopy, Parasitology, Plasmodium, Pregnancy, Pregnancy Complications, Infectious, Sensitivity and Specificity, Specimen Handling, Time Factors, Protozoan Proteins, Polymerase Chain Reaction, Young Adult
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