Inter-rater reliability of malaria parasite counts and comparison of methods

BACKGROUND: The introduction of artemesinin-based treatment for falciparum malaria has led to a shift away from symptom-based diagnosis. Diagnosis may be achieved by using rapid non-microscopic diagnostic tests (RDTs), of which there are many available. Light microscopy, however, has a central role in parasite identification and quantification and remains the main method of parasite-based diagnosis in clinic and hospital settings and is necessary for monitoring the accuracy of RDTs. The World Health Organization has prepared a proficiency testing panel containing a range of malaria-positive blood samples of known parasitaemia, to be used for the assessment of commercially available malaria RDTs. Different blood film and counting methods may be used for this purpose, which raises questions regarding accuracy and reproducibility. A comparison was made of the established methods for parasitaemia estimation to determine which would give the least inter-rater and inter-method variation METHODS: Experienced malaria microscopists counted asexual parasitaemia on different slides using three methods; the thin film method using the total erythrocyte count, the thick film method using the total white cell count and the Earle and Perez method. All the slides were stained using Giemsa pH 7.2. Analysis of variance (ANOVA) models were used to find the inter-rater reliability for the different methods. The paired t-test was used to assess any systematic bias between the two methods, and a regression analysis was used to see if there was a changing bias with parasite count level. RESULTS: The thin blood film gave parasite counts around 30% higher than those obtained by the thick film and Earle and Perez methods, but exhibited a loss of sensitivity with low parasitaemia. The thick film and Earle and Perez methods showed little or no bias in counts between the two methods, however, estimated inter-rater reliability was slightly better for the thick film method. CONCLUSION: The thin film method gave results closer to the true parasite count but is not feasible at a parasitaemia below 500 parasites per microlitre. The thick film method was both reproducible and practical for this project. The determination of malarial parasitaemia must be applied by skilled operators using standardized techniques

Inter-rater reliability of malaria parasite counts and comparison of methods

Abstract Background The introduction of artemesinin-based treatment for falciparum malaria has led to a shift away from symptom-based diagnosis. Diagnosis may be achieved by using rapid non-microscopic diagnostic tests (RDTs), of which there are many available. Light microscopy, however, has a central role in parasite identification and quantification and remains the main method of parasite-based diagnosis in clinic and hospital settings and is necessary for monitoring the accuracy of RDTs. The World Health Organization has prepared a proficiency testing panel containing a range of malaria-positive blood samples of known parasitaemia, to be used for the assessment of commercially available malaria RDTs. Different blood film and counting methods may be used for this purpose, which raises questions regarding accuracy and reproducibility. A comparison was made of the established methods for parasitaemia estimation to determine which would give the least inter-rater and inter-method variation Methods Experienced malaria microscopists counted asexual parasitaemia on different slides using three methods; the thin film method using the total erythrocyte count, the thick film method using the total white cell count and the Earle and Perez method. All the slides were stained using Giemsa pH 7.2. Analysis of variance (ANOVA) models were used to find the inter-rater reliability for the different methods. The paired t-test was used to assess any systematic bias between the two methods, and a regression analysis was used to see if there was a changing bias with parasite count level. Results The thin blood film gave parasite counts around 30% higher than those obtained by the thick film and Earle and Perez methods, but exhibited a loss of sensitivity with low parasitaemia. The thick film and Earle and Perez methods showed little or no bias in counts between the two methods, however, estimated inter-rater reliability was slightly better for the thick film method. Conclusion The thin film method gave results closer to the true parasite count but is not feasible at a parasitaemia below 500 parasites per microlitre. The thick film method was both reproducible and practical for this project. The determination of malarial parasitaemia must be applied by skilled operators using standardized techniques.</p

Can Maternal Exposure to Air Pollution Affect Post-Natal Liver Development?

Emerging evidence suggests that inhalation of particulate matter (PM) can have direct adverse effects on liver function. Early life is a time of particular vulnerability to the effects of air pollution. On that basis, we tested whether in utero exposure to residential PM has an impact on the developing liver. Pregnant mice (C57BL/6J) were intranasally administered 100 µg of PM sampled from residential roof spaces (~5 mg/kg) on gestational days 13.5, 15.5, and 17.5. The pups were euthanized at two weeks of age, and liver tissue was collected to analyse hepatic metabolism (glycogen storage and lipid level), cellular responses (oxidative stress, inflammation, and fibrosis), and genotoxicity using a range of biochemical assays, histological staining, ELISA, and qPCR. We did not observe pronounced effects of environmentally sampled PM on the developing liver when examining hepatic metabolism and cellular response. However, we did find evidence of liver genomic DNA damage in response to in utero exposure to PM. This effect varied depending on the PM sample. These data suggest that in utero exposure to real-world PM during mid-late pregnancy has limited impacts on post-natal liver development

Evaluation of the intra- and inter-specific genetic variability of <it>Plasmodium </it>lactate dehydrogenase

Abstract Background Malaria diagnosis is vital to efficient control programmes and the recent advent of malaria rapid diagnostic tests (RDTs) provides a reliable and simple diagnostic method. However a characterization of the efficiency of these tests and the proteins they detect is needed to maximize RDT sensitivity. Methods Plasmodial lactate dehydrogenase (pLDH) gene of wild isolates of the four human species of Plasmodium from a variety of malaria endemic settings were sequenced and analysed. Results No variation in nucleotide was found within Plasmodium falciparum, synonymous mutations were found for Plasmodium malariae and Plasmodium. vivax; and three different types of amino acid sequence were found for Plasmodium ovale. Conserved and variable regions were identified within each species. Conclusion The results indicate that antigen variability is unlikely to explain variability in performance of RDTs detecting pLDH from cases of P. falciparum, P. vivax or P. malariae malaria, but may contribute to poor detection of P. ovale.</p

Enterovirus 74 infection in children.

Enterovirus 74 (EV74) is a rarely detected viral infection of children. In 2010, EV74 was identified in New Zealand in a 2 year old child with acute flaccid paralysis (AFP) through routine polio AFP surveillance. A further three cases of EV74 were identified in children within six months. These cases are the first report of EV74 in New Zealand. In this study we describe the near complete genome sequence of four EV74 isolates from New Zealand, which shows only limited sequence identity in the non-structural proteins when compared to the other two known EV74 sequences. As is typical of enteroviruses multiple recombination events were evident, particularly in the P2 region and P3 regions. This is the first complete EV74 genome sequenced from a patient with acute flaccid paralysis

The proteomic response is linked to regional lung volumes in ventilator-induced lung injury

It is unclear how acid-induced lung injury alters the regional lung volume response to mechanical ventilation (MV) and how this impacts protein expression. Using a mouse model, we investigated the separate and combined effects of acid aspiration and MV on regional lung volumes and how these were associated with the proteome. Adult BALB/c mice were divided into four groups: intratracheal saline, intratracheal acid, saline/MV, or acid/MV. Specific tidal volume (sVt) and specific end-expiratory volume (sEEV) were measured at baseline and after 2 h of ventilation using dynamic high-resolution four-dimensional computed tomography (4DCT) images. Lung tissue was dissected into 10 regions corresponding to the image segmentation for label-free quantitative proteomic analysis. Our data showed that acid aspiration significantly reduced sVt and caused further reductions in sVt and sEEV after 2 h of ventilation. Proteomic analysis revealed 42 dysregulated proteins in both Saline/MV and Acid/MV groups, and 37 differentially expressed proteins in the Acid/MV group. Mapping of the overlapping proteins showed significant enrichment of complement/coagulation cascades (CCC). Analysis of 37 unique proteins in the Acid/MV group identified six additional CCC proteins and seven downregulated proteins involved in the mitochondrial respiratory chain (MRC). Regional MRC protein levels were positively correlated with sEEV, while the CCC protein levels were negatively associated with sVt. Therefore, this study showed that tidal volume was associated with the expression of CCC proteins, while low end-expiratory lung volumes were associated with MRC protein expression, suggesting that tidal stretch and lung collapse activate different injury pathways.NEW & NOTEWORTHY This study provides novel insights into the regional response to mechanical ventilation in the setting of acid-induced lung injury and highlights the complex interaction between tidal stretch and low-end-expiratory lung volumes; both of which caused altered regulation of different injury pathways

The link between regional tidal stretch and lung injury during mechanical ventilation

The aim of this study was to assess the association between regional tidal volume (Vt), regional functional residual capacity (FRC), and the expression of genes linked with ventilator-induced lung injury. Two groups of BALB/c mice (n = 8 per group) were ventilated for 2 hours using a protective or injurious ventilation strategy, with free-breathing mice used as control animals. Regional Vt and FRC of the ventilated mice was determined by analysis of high-resolution four-dimensional computed tomographic images taken at baseline and after 2 hours of ventilation and corrected for the volume of the region (i.e., specific [s]Vt and specific [s]FRC). RNA concentrations of 21 genes in 10 different lung regions were quantified using a quantitative PCR array. sFRC at baseline varied regionally, independent of ventilation strategy, whereas sVt varied regionally depending on ventilation strategy. The expression of IL-6 (P = 0.04), Ccl2 (P < 0.01), and Ang-2 (P < 0.05) was associated with sVt but not sFRC. The expression of seven other genes varied regionally (IL-1β and RAGE [receptor for advanced glycation end products]) or depended on ventilation strategy (Nfe2l2 [nuclear factor erythroid-derived 2 factor 2], c-fos, and Wnt1) or both (TNF-α and Cxcl2), but it was not associated with regional sFRC or sVt. These observations suggest that regional inflammatory responses to mechanical ventilation are driven primarily by tidal stretch