Reader technique as a source of variability in determining malaria parasite density by microscopy

O’Meara, Wendy Prudhomme; Barcus, Mazie J.; Wongsrichanalai, Chansuda; Muth, Sinuon; Maguire, Jason D.; Jordan, Robert G.; Prescott, William R.; McKenzie, F. Ellis

doi:10.1186/1475-2875-5-118

Cited by 69 publications

(66 citation statements)

References 13 publications

(14 reference statements)

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“…Microscopic detection of malaria parasites on Giemsa-stained blood smears is still considered the gold standard method for malaria diagnosis, clinical trials efficacy evaluation and epidemiological surveys. However, microscopy has numerous limitations such as low sensitivity, difficulties in quality control and standardization, operator dependence, poor specificity, and the need for continued training and evaluation [4,6,23,24]. Identification of parasites specific antigens, antibodies and nucleic acid sequences form the basis of established and novel diagnostic modalities.…”

Section: Discussionmentioning

confidence: 99%

Comparative evaluation of published real-time PCR assays for the detection of malaria following MIQE guidelines

Alemayehu

Feghali

Cowden

et al. 2013

Malar J

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BackgroundThe use of malaria-specific quantitative real-time PCR (qPCR) is increasing due to its high sensitivity, speciation and quantification of malaria parasites. However, due to the lack of consensus or standardized methods in performing qPCR, it is difficult to evaluate and/or compare the quality of work reported by different authors for a cross-study and/or cross-platform assay analysis.MethodsThe performances of seven published qPCR assays that detect Plasmodium spp or Plasmodium falciparum were compared using standard DNA and samples from a clinical trial. Amplification and qPCR measurements were performed using the Applied Biosystems 7500 Fast Real-Time PCR System. All the analyses were automatically established using the default settings. For the TaqMan probe format, the assays were performed in the background of QuantiFast Probe Master Mix whereas in SYBR Green format, the assays were performed in the background of QuantiFast SYBR Green Master Mix and QuantiTect SYBR Green Master Mix background.ResultsAssays with high PCR efficiencies outperformed those with low efficiencies in all categories including sensitivity, precision and consistency regardless of the assay format and background. With the exception of one assay, all assays evaluated showed lower sensitivity compared to what have been published. When samples from a malaria challenge study were analysed, the qPCR assay with the overall best performance detected parasites in subjects earliest and with most consistency.ConclusionThe data demonstrate the need for increased consensus and guidelines that will encourage better experimental practices, allowing more consistent and unambiguous interpretation of qPCR results.

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Section: Discussionmentioning

confidence: 99%

Comparative evaluation of published real-time PCR assays for the detection of malaria following MIQE guidelines

Alemayehu

Feghali

Cowden

et al. 2013

Malar J

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“…O’Meara et al [19] have shown that parasitaemia from the thick smear averaged 10% lower than the total mean ( p = 0.001) and they have also shown that white blood cells were much less uniformly distributed that the parasites. They also confirmed that up to 60% of parasites were obscured in the thick film or lost during the process of red cell lyses and parasite staining.…”

Section: Discussionmentioning

confidence: 99%

Inter-observer agreement according to malaria parasite density

Billo¹,

Diakité

Dolo

et al. 2013

Malar J

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BackgroundRecent developments in diagnostic techniques for malaria, particularly DNA probes and sero-immunology, have raised questions as to how these techniques might be used to facilitate malaria diagnosis at the most peripheral levels of the primary health care system. At present, malaria diagnosis is based on the standard microscopic examination of blood films in most field epidemiologic studies and is likely to remain so in the immediate future in Africa. The objective of this study was to assess inter-observer agreement for the examination of Giemsa-stained slides for Plasmodium falciparum parasites.MethodsChildren aged 0 to 10 years were enrolled yearly in Bancoumana village (West Africa), mainly during the transmission season (June to October). The blood smears obtained from the persistently negative children in June 1996, August 1996, October 1996 and March 1997 were systematically re-examined. A stratified random sample (10%) proportional to the following parasite density classes 1–100, 101–5000, and 5001 and over was taken from the slides collected. The kappa statistics and the intra-class correlation were used as measures of agreement the first and the second slide examinations.ResultsThe weighted kappa statistic, widely used as a chance-corrected measure for nominal agreement, showed excellent inter-observer agreement (κw=0.7926; 95% CI [0.7588, 0.8263]; p=0.01). The intra-class correlation co-efficient had the same value of 0.7926 confirming the appropriateness of the weighted kappa statistic. Inter-observer agreement for slides read as negative by one observer, or as containing more than 100 parasites per μl, was excellent: 97% (493/506) and 92% (145/158), respectively. In contrast, the inter-observer agreement for slides read by one observer as containing 1–100 parasites/μl was poor, 36% (96/268).ConclusionsIn field conditions in Mali, there was a high reproducibility for slides reported as negative or as having more than 100 parasites per μl. However, smears with readings of 1–100 parasites per μl were less reproducible and should be re-examined carefully.

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“…WHO training materials are still widely used, although an update is necessary. [17,18] Improving diagnostic accuracy in malaria control systems can be both technically and financially challenging. [19] Continued supervision and support are essential to ensure sustainability of accurate diagnosis and thereby appropriate treatment.…”

Section: Discussionmentioning

confidence: 99%

Diagnosis of malaria in red sea state, Sudan

Ageep¹

2013

Ann Trop Med Public Health

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Background: Malaria is one of the world killers, but it is curable disease if patients have access to early diagnosis and prompt treatment. The aims of this study are to estimate the frequency of malaria cases among febrile patients, to evaluate the frequency of the parasite species, and to detect the best method for diagnosis of malaria in Red Sea State, Sudan. Materials and Methods: This study was carried out in laboratory of the Red Sea Medical center, Port Sudan, Sudan in period from July 2005 to May 2011. Blood samples were collected from 9,670 febrile patients suspected to have malaria and were examined by expert technologists under the supervision of senior pathologist. Another 717 blood samples seen in peripheral laboratories by routine microscopy were sent for confirmation by expert microscopy. Rapid diagnostic tests (RDT) were also done to these blood samples. Results: Out of the 9,670 febrile patients, only 283 had malaria by expert microscopy. The commonest plasmodium specie that causes malaria in the region was P. falciparum (50.2%), followed by P. vivax (43.8%). The specificity of routine microscopy was (52.7%) and that for RDT was (90.4%). The sensitivity of routine microscopy was (98.6%) while that for RDT was (99.8%). Conclusions: Small number of patients complaining of fever had malaria in Red Sea State with P. falciparum representing (50.2%), followed by P. vivax (43.8%). RDT is recommended for diagnosis of malaria in our region.

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Reader technique as a source of variability in determining malaria parasite density by microscopy

Cited by 69 publications

References 13 publications

Comparative evaluation of published real-time PCR assays for the detection of malaria following MIQE guidelines

Comparative evaluation of published real-time PCR assays for the detection of malaria following MIQE guidelines

Inter-observer agreement according to malaria parasite density

Diagnosis of malaria in red sea state, Sudan

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