Haemoglobin thresholds to define anaemia from age 6 months to 65 years: estimates from international data sources.

BACKGROUND: Detection of anaemia is crucial for clinical medicine and public health. Current WHO anaemia definitions are based on statistical thresholds (fifth centiles) set more than 50 years ago. We sought to establish evidence for the statistical haemoglobin thresholds for anaemia that can be applied globally and inform WHO and clinical guidelines. METHODS: In this analysis we identified international data sources from populations in the USA, England, Australia, China, the Netherlands, Canada, Ecuador, and Bangladesh with sufficient clinical and laboratory information collected between 1998 and 2020 to obtain a healthy reference sample. Individuals with clinical or biochemical evidence of a condition that could reduce haemoglobin concentrations were excluded. We estimated haemoglobin thresholds (ie, 5th centiles) for children aged 6-23 months, 24-59 months, 5-11 years, and 12-17 years, and adults aged 18-65 years (including during pregnancy) for individual datasets and pooled across data sources. We also collated findings from three large-scale genetic studies to summarise genetic variants affecting haemoglobin concentrations in different ancestral populations. FINDINGS: We identified eight data sources comprising 18 individual datasets that were eligible for inclusion in the analysis. In pooled analyses, the haemoglobin fifth centile was 104·4 g/L (90% CI 103·5-105·3) in 924 children aged 6-23 months, 110·2 g/L (109·5-110·9) in 1874 children aged 24-59 months, and 114·4 g/L (113·6-115·2) in 1839 children aged 5-11 years. Values diverged by sex in adolescents and adults. In pooled analyses, the fifth centile was 122·2 g/L (90% CI 121·3-123·1) in 1741 female adolescents aged 12-17 years and 128·2 g/L (126·4-130·0) in 1103 male adolescents aged 12-17 years. In pooled analyses of adults aged 18-65 years, the fifth centile was 119·7 g/L (90% CI 119·1-120·3) in 3640 non-pregnant females and 134·9 g/L (134·2-135·6) in 2377 males. Fifth centiles in pregnancy were 110·3 g/L (90% CI 109·5-111·0) in the first trimester (n=772) and 105·9 g/L (104·0-107·7) in the second trimester (n=111), with insufficient data for analysis in the third trimester. There were insufficient data for adults older than 65 years. We did not identify ancestry-specific high prevalence of non-clinically relevant genetic variants that influence haemoglobin concentrations. INTERPRETATION: Our results enable global harmonisation of clinical and public health haemoglobin thresholds for diagnosis of anaemia. Haemoglobin thresholds are similar between sexes until adolescence, after which males have higher thresholds than females. We did not find any evidence that thresholds should differ between people of differering ancestries. FUNDING: World Health Organization and the Bill & Melinda Gates Foundation.

Breathing control training for functional seizures: A multi-site, open-label pilot study.

There are no well-validated treatments for functional seizures. While specialist psychotherapy is usually recommended, the evidence for its benefit is qualified, and it can be difficult to obtain. Given the association between hyperventilation and functional seizures we explored an alternative modality, breathing control training, in a multi-site open label pilot trial. Participants with functional seizures over the age of 16 received an hour of breathing training from a respiratory physiotherapist, with a half-hour booster session a month later. Seizure frequency and Nijmegen scores (a measure of hyperventilation) were reported at baseline and follow-up, 3-4 months later. Eighteen subjects were recruited, and 10 completed follow-up. Seven of these 10 had improved seizure frequency, and 3 did not (Wilcoxon signed rank test, p = 0.09), with seizure frequency correlating with Nijmegen score (Spearman's rank correlation = 0.75, p = 0.034). The intervention was well tolerated, with no adverse events reported. These preliminary results support a potentially new approach to treating functional seizures that should prove cost-effective and acceptable, though require confirmation by a randomised controlled trial.

Interim results from a phase I randomized, placebo-controlled trial of novel SARS-CoV-2 beta variant receptor-binding domain recombinant protein and mRNA vaccines as a 4th dose booster.

BACKGROUND: SARS-CoV-2 booster vaccination should ideally enhance protection against variants and minimise immune imprinting. This Phase I trial evaluated two vaccines targeting SARS-CoV-2 beta-variant receptor-binding domain (RBD): a recombinant dimeric RBD-human IgG1 Fc-fusion protein, and an mRNA encoding a membrane-anchored RBD. METHODS: 76 healthy adults aged 18-64 y, previously triple vaccinated with licensed SARS-CoV-2 vaccines, were randomised to receive a 4th dose of either an adjuvanted (MF59®, CSL Seqirus) protein vaccine (5, 15 or 45 µg, N = 32), mRNA vaccine (10, 20, or 50 µg, N = 32), or placebo (saline, N = 12) at least 90 days after a 3rd boost vaccination or SARS-CoV-2 infection. Bleeds occurred on days 1 (prior to vaccination), 8, and 29. CLINICALTRIALS: govNCT05272605. FINDINGS: No vaccine-related serious or medically-attended adverse events occurred. The protein vaccine reactogenicity was mild, whereas the mRNA vaccine was moderately reactogenic at higher dose levels. Best anti-RBD antibody responses resulted from the higher doses of each vaccine. A similar pattern was seen with live virus neutralisation and surrogate, and pseudovirus neutralisation assays. Breadth of immune response was demonstrated against BA.5 and more recent omicron subvariants (XBB, XBB.1.5 and BQ.1.1). Binding antibody titres for both vaccines were comparable to those of a licensed bivalent mRNA vaccine. Both vaccines enhanced CD4+ and CD8+ T cell activation. INTERPRETATION: There were no safety concerns and the reactogenicity profile was mild and similar to licensed SARS-CoV-2 vaccines. Both vaccines showed strong immune boosting against beta, ancestral and omicron strains. FUNDING: Australian Government Medical Research Future Fund, and philanthropies Jack Ma Foundation and IFM investors.

Study protocol for TARGET protein: The effect of augmented administration of enteral protein to critically ill adults on clinical outcomes: A cluster randomised, cross-sectional, double cross-over, clinical trial.

Background: It is unknown whether increasing dietary protein to 1.2-2.0 g/kg/day as recommended in international guidelines compared to current practice improves outcomes in intensive care unit (ICU) patients. The TARGET Protein trial will evaluate this. Objective: To describe the study protocol for the TARGET Protein trial. Design setting and participants: TARGET Protein is a cluster randomised, cross-sectional, double cross-over, pragmatic clinical trial undertaken in eight ICUs in Australia and New Zealand. Each ICU will be randomised to use one of two trial enteral formulae for three months before crossing over to the other formula, which is then repeated, with enrolment continuing at each ICU for 12 months. All patients aged ≥16 years in their index ICU admission commencing enteral nutrition will be eligible for inclusion. Eligible patients will receive the trial enteral formula to which their ICU is allocated. The two trial enteral formulae are isocaloric with a difference in protein dose: intervention 100g/1000 ml and comparator 63g/1000 ml. Staggered recruitment commenced in May 2022. Main outcomes measures: The primary outcome is days free of the index hospital and alive at day 90. Secondary outcomes include days free of the index hospital at day 90 in survivors, alive at day 90, duration of invasive ventilation, ICU and hospital length of stay, incidence of tracheostomy insertion, renal replacement therapy, and discharge destination. Conclusion: TARGET Protein aims to determine whether augmented enteral protein delivery reduces days free of the index hospital and alive at day 90. Trial registration: Australian New Zealand Clinical Trials Registry (ACTRN12621001484831).

Effect of adherence to primaquine on the risk of Plasmodium vivax recurrence: a WorldWide Antimalarial Resistance Network systematic review and individual patient data meta-analysis.

BACKGROUND: Imperfect adherence is a major barrier to effective primaquine radical cure of Plasmodium vivax. This study investigated the effect of reduced adherence on the risk of P. vivax recurrence. METHODS: Efficacy studies of patients with uncomplicated P. vivax malaria, including a treatment arm with daily primaquine, published between January 1999 and March 2020 were identified. Individual patient data from eligible studies were pooled using standardized methodology. Adherence to primaquine was inferred from i) the percentage of supervised doses and ii) the total mg/kg dose received compared to the target total mg/kg dose per protocol. The effect of adherence to primaquine on the incidence of P. vivax recurrence between days 7 and 90 was investigated by Cox regression analysis. RESULTS: Of 82 eligible studies, 32 were available including 6917 patients from 18 countries. For adherence assessed by percentage of supervised primaquine, 2790 patients (40.3%) had poor adherence (≤ 50%) and 4127 (59.7%) had complete adherence. The risk of recurrence by day 90 was 14.0% [95% confidence interval: 12.1-16.1] in patients with poor adherence compared to 5.8% [5.0-6.7] following full adherence; p = 0.014. After controlling for age, sex, baseline parasitaemia, and total primaquine dose per protocol, the rate of the first recurrence was higher following poor adherence compared to patients with full adherence (adjusted hazard ratio (AHR) = 2.3 [1.8-2.9]). When adherence was quantified by total mg/kg dose received among 3706 patients, 347 (9.4%) had poor adherence, 88 (2.4%) had moderate adherence, and 3271 (88.2%) had complete adherence to treatment. The risks of recurrence by day 90 were 8.2% [4.3-15.2] in patients with poor adherence and 4.9% [4.1-5.8] in patients with full adherence; p < 0.001. CONCLUSION: Reduced adherence, including less supervision, increases the risk of vivax recurrence.

Statistical haemoglobin thresholds to define anaemia across the lifecycle.

Detection of anaemia is critical for clinical medicine and public health. Current WHO values that define anaemia are statistical thresholds (5 th centile) set over 50 years ago, and are presently <110g/L in children 6-59 months, <115g/L in children 5-11 years, <110g/L in pregnant women, <120g/L in children 12-14 years of age, <120g/L in non-pregnant women, and <130g/L in men. Haemoglobin is sensitive to iron and other nutrient deficiencies, medical illness and inflammation, and is impacted by genetic conditions; thus, careful exclusion of these conditions is crucial to obtain a healthy reference population. We identified data sources from which sufficient clinical and laboratory information was available to determine an apparently healthy reference sample. Individuals were excluded if they had any clinical or biochemical evidence of a condition that may diminish haemoglobin concentration. Discrete 5 th centiles were estimated along with two-sided 90% confidence intervals and estimates combined using a fixed-effect approach. Estimates for the 5 th centile of the healthy reference population in children were similar between sexes. Thresholds in children 6-23 months were 104.4g/L [90% CI 103.5, 105.3]; in children 24-59 months were 110.2g/L [109.5, 110.9]; and in children 5-11 years were 114.1g/L [113.2, 115.0]. Thresholds diverged by sex in adolescents and adults. In females and males 12-17 years, thresholds were 122.2g/L [121.3, 123.1] and 128.2 [126.4, 130.0], respectively. In adults 18-65 years, thresholds were 119.7g/L [119.1, 120.3] in non-pregnant females and 134.9g/L [134.2, 135.6] in males. Limited analyses indicated 5 th centiles in first-trimester pregnancy of 110.3g/L [109.5, 111.0] and 105.9g/L [104.0, 107.7] in the second trimester. All thresholds were robust to variations in definitions and analysis models. Using multiple datasets comprising Asian, African, and European ancestries, we did not identify novel high prevalence genetic variants that influence haemoglobin concentration, other than variants in genes known to cause important clinical disease, suggesting non-clinical genetic factors do not influence the 5 th centile between ancestries. Our results directly inform WHO guideline development and provide a platform for global harmonisation of laboratory, clinical and public health haemoglobin thresholds.

Ambulatory assessment to predict problem anger in trauma-affected adults: Study protocol.

BACKGROUND: Problem anger is common after experiencing a traumatic event. Current evidence-driven treatment options are limited, and problem anger negatively affects an individual's capacity to engage with traditional psychological treatments. Smartphone interventions hold significant potential in mental health because of their ability to deliver low-intensity, precision support for individuals at the time and place they need it most. While wearable technology has the capacity to augment smartphone-delivered interventions, there is a dearth of evidence relating to several key areas, including feasibility of compliance in mental health populations; validity of in vivo anger assessment; ability to predict future mood states; and delivery of timely and appropriate interventions. METHODS: This protocol describes a cohort study that leverages 10 days of ambulatory assessment in the form of ecological momentary assessment and a wearable. Approximately 100 adults with problem anger will complete four-hourly in vivo mobile application-delivered micro-surveys on anger intensity, frequency, and verbal and physical aggression, as well as other self-reported mental health and wellbeing measures. Concurrently, a commercial wearable device will continuously record indicators of physiological arousal. The aims are to test the feasibility and acceptability of ambulatory assessment in a trauma-affected population, and determine whether a continuously measured physiological indicator of stress predicts self-reported anger intensity. DISCUSSION: This study will contribute new data around the ability of physiological indicators to predict mood state in individuals with psychopathology. This will have important implications for the design of smartphone-delivered interventions for trauma-affected individuals, as well as for the digital mental health field more broadly.

How quickly does a wound heal? Bayesian calibration of a mathematical model of venous leg ulcer healing.

Chronic wounds, such as venous leg ulcers, are difficult to treat and can reduce the quality of life for patients. Clinical trials have been conducted to identify the most effective venous leg ulcer treatments and the clinical factors that may indicate whether a wound will successfully heal. More recently, mathematical modelling has been used to gain insight into biological factors that may affect treatment success but are difficult to measure clinically, such as the rate of oxygen flow into wounded tissue. In this work, we calibrate an existing mathematical model using a Bayesian approach with clinical data for individual patients to explore which clinical factors may impact the rate of wound healing for individuals. Although the model describes group-level behaviour well, it is not able to capture individual-level responses in all cases. From the individual-level analysis, we propose distributions for coefficients of clinical factors in a linear regression model, but ultimately find that it is difficult to draw conclusions about which factors lead to faster wound healing based on the existing model and data. This work highlights the challenges of using Bayesian methods to calibrate partial differential equation models to individual patient clinical data. However, the methods used in this work may be modified and extended to calibrate spatiotemporal mathematical models to multiple data sets, such as clinical trials with several patients, to extract additional information from the model and answer outstanding biological questions.

Comparison of Antibody Responses and Parasite Clearance in Artemisinin Therapeutic Efficacy Studies in the Democratic Republic of Congo and Asia.

BACKGROUND: Understanding the effect of immunity on Plasmodium falciparum clearance is essential for interpreting therapeutic efficacy studies designed to monitor emergence of artemisinin drug resistance. In low-transmission areas of Southeast Asia, where resistance has emerged, P. falciparum antibodies confound parasite clearance measures. However, variation in naturally acquired antibodies across Asian and sub-Saharan African epidemiological contexts and their impact on parasite clearance re yet to be quantified. METHODS: In an artemisinin therapeutic efficacy study, antibodies to 12 pre-erythrocytic and erythrocytic P. falciparum antigens were measured in 118 children with uncomplicated P. falciparum malaria in the Democratic Republic of Congo (DRC) and compared with responses in patients from Asian sites, described elsewhere. RESULTS: Parasite clearance half-life was shorter in DRC patients (median, 2 hours) compared with most Asian sites (median, 2-7 hours), but P. falciparum antibody levels and seroprevalences were similar. There was no evidence for an association between antibody seropositivity and parasite clearance half-life (mean difference between seronegative and seropositive, -0.14 to +0.40 hour) in DRC patients. CONCLUSIONS: In DRC, where artemisinin remains highly effective, the substantially shorter parasite clearance time compared with Asia was not explained by differences in the P. falciparum antibody responses studied.

Anti-Gametocyte Antigen Humoral Immunity and Gametocytemia During Treatment of Uncomplicated Falciparum Malaria: A Multi-National Study.

Introduction: Understanding the human immune response to Plasmodium falciparum gametocytes and its association with gametocytemia is essential for understanding the transmission of malaria as well as progressing transmission blocking vaccine candidates. Methods: In a multi-national clinical efficacy trial of artemisinin therapies (13 sites of varying transmission over South-East Asia and Africa), we measured Immunoglobulin G (IgG) responses to recombinant P. falciparum gametocyte antigens expressed on the gametocyte plasma membrane and leading transmission blocking vaccine candidates Pfs230 (Pfs230c and Pfs230D1M) and Pfs48/45 at enrolment in 1,114 participants with clinical falciparum malaria. Mixed effects linear and logistic regression were used to determine the association between gametocyte measures (gametocytemia and gametocyte density) and antibody outcomes at enrolment. Results: Microscopy detectable gametocytemia was observed in 11% (127/1,114) of participants at enrolment, and an additional 9% (95/1,114) over the follow-up period (up to day 42) (total 20% of participants [222/1,114]). IgG levels in response to Pfs230c, Pfs48/45 and Pfs230D1M varied across study sites at enrolment (p < 0.001), as did IgG seroprevalence for anti-Pfs230c and D1M IgG (p < 0.001), but not for anti-Pfs48/45 IgG (p = 0.159). In adjusted analyses, microscopy detectable gametocytemia at enrolment was associated with an increase in the odds of IgG seropositivity to the three gametocyte antigens (Pfs230c OR [95% CI], p: 1.70 [1.10, 2.62], 0.017; Pfs48/45: 1.45 [0.85, 2.46], 0.174; Pfs230D1M: 1.70 [1.03, 2.80], 0.037), as was higher gametocyte density at enrolment (per two-fold change in gametocyte density Pfs230c OR [95% CI], p: 1.09 [1.02, 1.17], 0.008; Pfs48/45: 1.05 [0.98, 1.13], 0.185; Pfs230D1M: 1.07 [0.99, 1.14], 0.071). Conclusion: Pfs230 and Pfs48/45 antibodies are naturally immunogenic targets associated with patent gametocytemia and increasing gametocyte density across multiple malaria endemic settings, including regions with emerging artemisinin-resistant P. falciparum.

Quantification of the dynamics of antibody response to malaria to inform sero-surveillance in pregnant women.

BACKGROUND: Malaria remains a major public health threat and tools sensitive to detect infections in low malaria transmission areas are needed to progress elimination efforts. Pregnant women are particularly vulnerable to malaria infections. Throughout pregnancy they access routine antenatal care, presenting a unique sentinel population to apply novel sero-surveillance tools to measure malaria transmission. The aim of this study was to quantify the dynamic antibody responses to multiple antigens during pregnancy so as to identify a single or multiple antibody response of exposure to malaria in pregnancy. METHODS: This study involved a secondary analysis of antibody responses to six parasite antigens [five commonly studied merozoite antigens and the variant surface antigen 2-chondroitin sulphate A (VAR2CSA), a pregnancy-specific erythrocytic antigen] measured by enzyme-linked immunosorbent assay (ELISA) over the gestation period until delivery (median of 7 measurements/woman) in 250 pregnant women who attended antenatal clinics located at the Thai-Myanmar border. A multivariate mixture linear mixed model was used to cluster the pregnant women into groups that have similar longitudinal antibody responses to all six antigens over the gestational period using a Bayesian approach. The variable-specific entropy was calculated to identify the antibody responses that have the highest influence on the classification of the women into clusters, and subsequent agreement with grouping of women based on exposure to malaria during pregnancy. RESULTS: Of the 250 pregnant women, 135 had a Plasmodium infection detected by light microscopy during pregnancy (39% Plasmodium falciparum only, 33% Plasmodium vivax only and 28% mixed/other species), defined as cases. The antibody responses to all six antigens accurately identified the women who did not have a malaria infection detected during pregnancy (93%, 107/115 controls). Antibody responses to P. falciparum merozoite surface protein 3 (PfMSP3) and P. vivax apical membrane antigen 1 (PvAMA1) were the least dynamic. Antibody responses to the antigens P. falciparum apical membrane antigen 1 (PfAMA1) and PfVAR2CSA were able to identify the majority of the cases more accurately (63%, 85/135). CONCLUSION: These findings suggest that the combination of antibodies, PfAMA1 and PfVAR2CSA, may be useful for sero-surveillance of malaria infections in pregnant women, particularly in low malaria transmission settings. Further investigation of other antibody markers is warranted considering these antibodies combined only detected 63% of the malaria infections during pregnancy.

Association of menstrual cycle and postoperative quality of recovery in premenopausal women: a prospective cohort study.

Background: Women have poorer quality of postoperative recovery from general anaesthesia than men. This persists for at least 3 days postoperatively, and is more pronounced in premenopausal women. Studies of menstrual cycle effects on pain or postoperative nausea and vomiting report conflicting results. Our aim was to determine whether menstrual cycle phase is associated with quality of recovery after surgery in premenopausal women. Methods: Eligible women aged 18-45 yr undergoing wisdom teeth extraction or laparoscopic cholecystectomy under general anaesthesia with volatile agents were recruited from Epworth HealthCare Richmond in Melbourne, Australia from 2019 to 2021. Menstrual history and progesterone levels were used to determine cycle phase (luteal or non-luteal). Linear mixed and generalised linear regression models were fitted to examine differences in Quality of Recovery-15 (QoR-15) score on postoperative days 1 (primary outcome) and 3, and secondary outcomes (pain, analgesic effectiveness, postoperative nausea and vomiting, prolonged hospital admission), between groups, adjusting for confounders. Results: A total of 177 women were recruited (74 luteal, 103 non-luteal). Six (3%) underwent laparoscopic cholecystectomy. Estimated mean differences (95% confidence interval; P-value) in adjusted QoR-15 scores between luteal and non-luteal groups were -0.05 (-5.86 to 5.76; P=0.986) and 1.40 (-4.41 to 7.21; P=0.636) on postoperative days 1 and 3, respectively. Secondary outcomes were not different between groups. Conclusions: There was no significant difference in postoperative QoR-15 score or other outcomes between women in the luteal and non-luteal phases of their cycle. Women can be reassured that cycle phase does not impact postoperative quality of recovery when undergoing minor surgery under general anaesthesia. Clinical trial registration: ACTRN12618000240246.

Scoping Review of Antimalarial Drug Candidates in Phase I and II Drug Development.

The emergence and spread of parasite resistance to currently available antimalarials has highlighted the importance of developing novel antimalarials. This scoping review provides an overview of antimalarial drug candidates undergoing phase I and II studies between 1 January 2016 and 28 April 2021. PubMed, Web of Science, Embase, clinical trial registries, and reference lists were searched for relevant studies. Information regarding antimalarial compound details, clinical trial characteristics, study population, and drug pharmacokinetics and pharmacodynamics (PK-PD) were extracted. A total of 50 studies were included, of which 24 had published their results and 26 were unpublished. New antimalarial compounds were evaluated as monotherapy (28 studies, 14 drug candidates) and combination therapy (9 studies, 10 candidates). Fourteen active compounds were identified in the current antimalarial drug development pipeline together with 11 compounds that are inactive, 6 due to insufficient efficacy. PK-PD data were available from 24 studies published as open-access articles. Four unpublished studies have made their results publicly available on clinical trial registries. The terminal elimination half-life of new antimalarial compounds ranged from 14.7 to 483 h. The log10 parasite reduction ratio over 48 h and parasite clearance half-life for Plasmodium falciparum following a single-dose monotherapy were 1.55 to 4.1 and 3.4 to 9.4 h, respectively. The antimalarial drug development landscape has seen a number of novel compounds, with promising PK-PD properties, evaluated in phase I and II studies over the past 5 years. Timely public disclosure of PK-PD data is crucial for informative decision-making and drug development strategy.

Seeking an optimal dosing regimen for OZ439/DSM265 combination therapy for treating uncomplicated falciparum malaria.

BACKGROUND: The efficacy of artemisinin-based combination therapies (ACTs), the first-line treatments for uncomplicated falciparum malaria, has been declining in malaria-endemic countries due to the emergence of malaria parasites resistant to these compounds. Novel alternative therapies are needed urgently to prevent the likely surge in morbidity and mortality due to failing ACTs. OBJECTIVES: This study investigates the efficacy of the combination of two novel drugs, OZ439 and DSM265, using a biologically informed within-host mathematical model. METHODS: A within-host model was developed, which accounts for the differential killing of these compounds against different stages of the parasite's life cycle and accommodates the pharmacodynamic interaction between the drugs. Data of healthy volunteers infected with falciparum malaria collected from four trials (three that administered OZ439 and DSM265 alone, and the fourth a combination of OZ439 and DSM265) were analysed. Model parameters were estimated in a hierarchical Bayesian framework. RESULTS: The posterior predictive simulations of our model predicted that 800 mg of OZ439 combined with 450 mg of DSM265, which are within the safe and tolerable dose range, can provide above 90% cure rates 42 days after drug administration. CONCLUSIONS: Our results show that the combination of OZ439 and DSM265 can be a promising alternative to replace ACTs. Our model can be used to inform future Phase 2 and 3 clinical trials of OZ439/DSM265, fast-tracking the deployment of this combination therapy in the regions where ACTs are failing. The dosing regimens that are shown to be efficacious and within safe and tolerable limits are suggested for future investigations.

Community-based molecular and serological surveillance of subclinical malaria in Myanmar.

BACKGROUND: In the Greater Mekong Subregion (GMS), current malaria surveillance strategies rely on a network of village health volunteers (VHVs) reporting the results of rapid diagnostic tests (RDTs), known to miss many asymptomatic infections. Integration of more sensitive diagnostic molecular and serological measures into the VHV network may improve surveillance of residual malaria transmission in hard-to-reach areas in the region and inform targeted interventions and elimination responses. However, data on residual malaria transmission that would be captured by these measures in the VHV-led testing and treatment surveillance network in the GMS is unknown. METHODS: A total of 114 VHVs were trained to collect dried blood spots from villagers undergoing routine RDTs as part of VHV-led active and passive case detection from April 2015 to June 2016. Samples were subjected to molecular testing (quantitative polymerase chain reaction [qPCR]) to determine Plasmodium falciparum and P. vivax infection and serological testing (against P. falciparum and P. vivax antigens) to determine exposure to P. falciparum and P. vivax. RESULTS: Over 15 months, 114 VHVs performed 32,194 RDTs and collected samples for molecular (n = 13,157) and serological (n = 14,128) testing. The prevalence of molecular-detectable P. falciparum and P. vivax infection was 3.2% compared to the 0.16% prevalence of Plasmodium spp. by RDT, highlighting the large burden of infections undetected by standard surveillance. Peaks in anti-P. falciparum, but not P. vivax, merozoite IgG seroprevalence coincided with seasonal P. falciparum transmission peaks, even in those with no molecularly detectable parasites. At the individual level, antibody seropositivity was associated with reduced odds of contemporaneous P. falciparum (OR for PfCSP 0.51 [95%CI 0.35, 0.76], p = 0.001, PfAMA1 0.70 [95%CI 0.52, 0.93], p = 0.01, and PfMSP2 0.81 [95%CI 0.61, 1.08], p = 0.15), but not P. vivax infection (OR PvAMA1 1.02 [95%CI 0.73, 1.43], p = 0.89) indicating a potential role of immunity in protection against molecular-detectable P. falciparum parasitaemia. CONCLUSIONS: We demonstrated that integration and implementation of sample collection for molecular and serological surveillance into networks of VHV servicing hard-to-reach populations in the GMS is feasible, can capture significant levels of ongoing undetected seasonal malaria transmission and has the potential to supplement current routine RDT testing. Improving malaria surveillance by advancing the integration of molecular and serological techniques, through centralised testing approaches or novel point-of-contact tests, will advance progress, and tracking, towards malaria elimination goals in the GMS.

Development and Validation of an In Silico Decision Tool To Guide Optimization of Intravenous Artesunate Dosing Regimens for Severe Falciparum Malaria Patients.

Most deaths from severe falciparum malaria occur within 24 h of presentation to a hospital. Intravenous (i.v.) artesunate is the first-line treatment for severe falciparum malaria, but its efficacy may be compromised by delayed parasitological responses. In patients with severe malaria, the life-saving benefit of the artemisinin derivatives is their ability to clear circulating parasites rapidly, before they can sequester and obstruct the microcirculation. To evaluate the dosing of i.v. artesunate for the treatment of artemisinin-sensitive and reduced ring stage sensitivity to artemisinin severe falciparum malaria infections, Bayesian pharmacokinetic-pharmacodynamic modeling of data from 94 patients with severe malaria (80 children from Africa and 14 adults from Southeast Asia) was performed. Assuming that delayed parasite clearance reflects a loss of ring stage sensitivity to artemisinin derivatives, the median (95% credible interval) percentage of patients clearing ≥99% of parasites within 24 h (PC24≥99%) for standard (2.4 mg/kg body weight i.v. artesunate at 0 and 12 h) and simplified (4 mg/kg i.v. artesunate at 0 h) regimens was 65% (52.5% to 74.5%) versus 44% (25% to 61.5%) for adults, 62% (51.5% to 74.5%) versus 39% (20.5% to 58.5%) for larger children (≥20 kg), and 60% (48.5% to 70%) versus 36% (20% to 53.5%) for smaller children (<20 kg). The upper limit of the credible intervals for all regimens was below a PC24≥99% of 80%, a threshold achieved on average in clinical studies of severe falciparum malaria infections. In severe falciparum malaria caused by parasites with reduced ring stage susceptibility to artemisinin, parasite clearance is predicted to be slower with both the currently recommended and proposed simplified i.v. artesunate dosing regimens.

Parasite-Host Dynamics throughout Antimalarial Drug Development Stages Complicate the Translation of Parasite Clearance.

Ensuring continued success against malaria depends on a pipeline of new antimalarials. Antimalarial drug development utilizes preclinical murine and experimental human malaria infection studies to evaluate drug efficacy. A sequential approach is typically adapted, with results from each stage informing the design of the next stage of development. The validity of this approach depends on confidence that results from murine malarial studies predict the outcome of clinical trials in humans. Parasite clearance rates following treatment are key parameters of drug efficacy. To investigate the validity of forward predictions, we developed a suite of mathematical models to capture parasite growth and drug clearance along the drug development pathway and estimated parasite clearance rates. When comparing the three infection experiments, we identified different relationships of parasite clearance with dose and different maximum parasite clearance rates. In Plasmodium berghei-NMRI mouse infections, we estimated a maximum parasite clearance rate of 0.2 (1/h); in Plasmodium falciparum-SCID mouse infections, 0.05 (1/h); and in human volunteer infection studies with P. falciparum, we found a maximum parasite clearance rate of 0.12 (1/h) and 0.18 (1/h) after treatment with OZ439 and MMV048, respectively. Sensitivity analysis revealed that host-parasite driven processes account for up to 25% of variance in parasite clearance for medium-high doses of antimalarials. Although there are limitations in translating parasite clearance rates across these experiments, they provide insight into characterizing key parameters of drug action and dose response and assist in decision-making regarding dosage for further drug development.

Artemisinin Resistance and the Unique Selection Pressure of a Short-acting Antimalarial.

Resistance to the artemisinin derivatives, our most effective antimalarial drugs, has not manifest as a classical resistance phenotype in which parasites can tolerate higher drug concentrations. Instead, resistant parasites have an altered maturation. We hypothesize that the short half-life of artemisinin concentrations is an unanticipated driver of this novel resistance phenotype.

Transient childhood wheeze is associated with less atopy in adolescence.

BACKGROUND: The relationships between childhood wheeze phenotypes and subsequent allergic conditions other than asthma, including hay fever, eczema and sensitization, have not been widely reported. We aimed to investigate this relationship up to late adolescence. METHODS: Using five childhood wheeze phenotypes defined from 620 children in a high-atopy risk birth cohort (Melbourne Atopy Cohort Study), we investigated their relationships with sensitization, eczema, hay fever and fractional exhaled nitric oxide (FeNO) at ages 12 and/or 18 years using logistic and linear regression models. RESULTS: 'Early Persistent wheeze' was associated with the increased risk of eczema (odds ratio: 3.69; 95% CI: 1.23, 11.12) and sensitization (4.52; 1.50, 13.64) at 12 years. 'Intermediate Onset wheeze' was associated with the increased risk of eczema at 12 years (2.57; 1.11, 5.97), hay fever at 12 (2.87; 1.44, 5.74) and 18 years (2.19; 1.20, 4.02), sensitization at 12 (2.25; 1.17, 4.34) and 18 years (2.46; 1.18, 5.12), and raised FeNO at 18 years. 'Late Onset wheeze' was associated with the increased risk of hay fever at 12 (5.18; 1.11, 24.20) and 18 years (4.20; 1.03, 17.11) and sensitization at 12 years (3.27; 0.81, 13.27). In contrast, 'Early Transient wheeze' was associated with the reduced risk of eczema (0.44; 0.20, 0.96), hay fever (0.57; 0.33, 0.99) and sensitization (0.59; 0.35, 0.99) at 18 years and a lower FeNO compared with 'Never/Infrequent wheezers'. CONCLUSIONS: Persistent wheeze phenotypes were associated with allergic outcomes up to 18 years with 'Intermediate Onset wheeze' being the most atopic group. In contrast, 'Early Transient wheezers' had less risk of allergic outcomes at 18 years. This protective effect may reassure parents of wheezy infants and young children.

Malaria Parasite Clearance: What Are We Really Measuring?

Antimalarial drugs are vital for treating malaria and controlling transmission. Measuring drug efficacy in the field requires large clinical trials and thus we have identified proxy measures of drug efficacy such as the parasite clearance curve. This is often assumed to measure the rate of drug activity against parasites and is used to predict optimal treatment regimens required to completely clear a blood-stage infection. We discuss evidence that the clearance curve is not measuring the rate of drug killing. This has major implications for how we assess optimal treatment regimens, as well as how we prioritise new drugs in the drug development pipeline.