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Dive into the research topics where Daniel Hayes is active.

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Featured researches published by Daniel Hayes.


Statistics in Medicine | 2009

Estimating regional centile curves from mixed data sources and countries

S. van Buuren; Daniel Hayes; D.M. Stasinopoulos; Robert Rigby; F.O. ter Kuile; Dianne J Terlouw

Regional or national growth distributions can provide vital information on the health status of populations. In most resource poor countries, however, the required anthropometric data from purpose-designed growth surveys are not readily available. We propose a practical method for estimating regional (multi-country) age-conditional weight distributions based on existing survey data from different countries. We developed a two-step method by which one is able to model data with widely different age ranges and sample sizes. The method produces references both at the country level and at the regional (multi-country) level. The first step models country-specific centile curves by Box-Cox t and Box-Cox power exponential distributions implemented in generalized additive model for location, scale and shape through a common model. Individual countries may vary in location and spread. The second step defines the regional reference from a finite mixture of the country distributions, weighted by population size. To demonstrate the method we fitted the weight-for-age distribution of 12 countries in South East Asia and the Western Pacific, based on 273 270 observations. We modeled both the raw body weight and the corresponding Z score, and obtained a good fit between the final models and the original data for both solutions. We briefly discuss an application of the generated regional references to obtain appropriate, region specific, age-based dosing regimens of drugs used in the tropics. The method is an affordable and efficient strategy to estimate regional growth distributions where the standard costly alternatives are not an option.


Malaria Journal | 2014

Optimizing the programmatic deployment of the anti-malarials artemether-lumefantrine and dihydroartemisinin-piperaquine using pharmacological modelling

Eva Maria Hodel; Katherine Kay; Daniel Hayes; Dianne J Terlouw; Ian M. Hastings

BackgroundSuccessful programmatic use of anti-malarials faces challenges that are not covered by standard drug development processes. The development of appropriate pragmatic dosing regimens for low-resource settings or community-based use is not formally regulated, even though these may alter factors which can substantially affect individual patient and population level outcome, such as drug exposure, patient adherence and the spread of drug resistance and can affect a drug’s reputation and its eventual therapeutic lifespan.MethodsAn in silico pharmacological model of anti-malarial drug treatment with the pharmacokinetic/pharmacodynamic profiles of artemether-lumefantrine (AM-LF, Coartem®) and dihydroartemisinin-piperaquine (DHA-PPQ, Eurartesim®) was constructed to assess the potential impact of programmatic factors, including regionally optimized, age-based dosing regimens, poor patient adherence, food effects and drug resistance on treatment outcome at population level, and compared both drugs’ susceptibility to these factors.ResultsCompared with DHA-PPQ, therapeutic effectiveness of AM-LF seems more robust to factors affecting drug exposure, such as age- instead of weight-based dosing or poor adherence. The model highlights the sub-optimally low ratio of DHA:PPQ which, in combination with the narrow therapeutic dose range of PPQ compared to DHA that drives the weight or age cut-offs, leaves DHA at a high risk of under-dosing.ConclusionPharmacological modelling of real-life scenarios can provide valuable supportive data and highlight modifiable determinants of therapeutic effectiveness that can help optimize the deployment of anti-malarials in control programmes.


Bulletin of The World Health Organization | 2015

Developing regional weight-for-age growth references for malaria-endemic countries to optimize age-based dosing of antimalarials

Daniel Hayes; Stef van Buuren; Feiko O. ter Kuile; D. Mikis Stasinopoulos; Robert Rigby; Dianne J Terlouw

Abstract Objective To derive regional weight-for-age growth references to help optimize age-based dosing of antimalarials in Africa, the Americas, South-East Asia and the Western Pacific. Methods A weight-for-age database was constructed from pre-existing population-based anthropometric data obtained from household surveys and research groups. It contained data collected between 1995 and 2012 on 1 263 119 individuals (909 368 female, 353 751 male) older than 14 days and younger than 50 years in 64 malaria-endemic countries. Regional growth references were generated using a generalized additive model for location, scale and shape by combining data with varying distributions from a range of sources. Countries were weighted by their population at risk of malaria to enable references to be used in optimizing the dosing of antimalarials. Findings Large differences in weight-for-age distributions existed between the regions and between the regions and global growth standards. For example, the average adult male from the Americas weighed 68.1 kg – 6.0 kg more than males in South-East Asia and the Western Pacific (average: 62.1 kg). For adult women, the difference was over 10.4 kg: the average was 60.4 kg in the Americas and 50.0 kg in South-East Asia and the Western Pacific. Conclusion There were substantial variations in weight-for-age growth curves between malaria-endemic areas. The growth reference charts derived here can be used to guide the evidence-based optimization of aged-based dosing regimens for antimalarials and other drugs often prescribed by age.


Tropical Medicine & International Health | 2013

Practical dosing of praziquantel for schistosomiasis in preschool-aged children

Piero Olliaro; Michel Vaillant; Daniel Hayes; Antonio Montresor; Lester Chitsulo

Schistosomiasis is known to occur in preschool‐aged children, but achieving accurate dosing of praziquantel in its current form is challenging. While waiting for a paediatric formulation, there is a need to develop a means for using the available products to treat this age group. Current 600‐mg tablets are differently scored to give units of 150 mg (a quarter of a tablet) or 300 mg (half a tablet).


Malaria Journal | 2012

An in silico drug treatment model to assess the robustness of regional age-based dosing regimens for artemisinin-based combination therapies

Eva Maria Hodel; Katherine Kay; Daniel Hayes; Anja Terlouw; Ian M. Hastings

The standard drug development process for antimalarials and other drugs uses weight-based dosing (mg/kg) to predict blood concentrations of the drug, and hence their effect. Consequently, the current World Health Organization Guidelines for the treatment of malaria [1] provide target doses and therapeutic dose ranges in mg/ kg/day. However, in resource-poor settings, age-based dosing is often employed instead of weight-based dosing because of the scarcity of correctly functioning weighing scales outside of clinical settings. Due to the wide variation in weight by age this approach inevitably results in over- and under-dosing of a proportion of the population. We have recently developed a modelling method to create statistically robust global and regional malaria-specific weight-for-age references representative of the malaria-endemic countries [2] and employed it to predict optimized age-based regimens for artemisinin-based combination therapies (ACTs) for case management of uncomplicated malaria (unpublished). The presented work now assesses the robustness of these age-based regimens using an in silico model of antimalarial drug treatment to predict treatment outcome based on individual infection parameters such as parasite numbers, variation in patient pharmacokinetics, and parasite variation in their drug sensitivity [3]. This extended pharmacokinetic/pharmakodynamic model for ACTs allowed us to investigate extreme treatment scenarios in a large number of patients over long follow-up periods that for ethical reasons could not be applied in clinical trials: typical examples include poor adherence (e.g. delayed, reduced or missed doses) or administration of doses above or below recommended therapeutic dose ranges and particularly in most vulnerable individuals such as infants and young children. Pharmacological modelling of antimalarial treatment cannot replace the gold standard of clinical trials, but the model outputs can identify patient groups that are at higher risk of treatment failure due to under-dosing or adverse events due to over-dosing. We acknowledge the Medical Research Council for funding of this work.


BMC Infectious Diseases | 2017

Modelling the therapeutic dose range of single low dose primaquine to reduce malaria transmission through age-based dosing

Daniel Hayes; Clifford George Banda; Alexandra Chipasula-Teleka; Dianne J Terlouw


Archive | 2015

Developing regional weight-for-age growth references to optimize age-based dosing of antimalarials

Daniel Hayes; Stef van Buuren; Feiko terKuile; D. Mikis Stasinopoulos; Robert Rigby; Anja Terlouw


Archive | 2018

Geostatistical modelling of the relationship between malaria and child growth in Africa

Benjamin Amoah; Emanuele Giorgi; Daniel Hayes; Stef van Buuren; Peter J. Diggle


Archive | 2009

Regional weight-for-age growth references for malaria endemic areas in Africa, Asia and Latin America to improve age-based dosing

Daniel Hayes; S. van Buuren; Feiko O. ter Kuile; Mikis Stasinopoulos; Robert Rigby; Anja Terlouw


Archive | 2008

Regional Age-Based Dose Regimens for a New Fixed-Dose Combination of Artesunate-Mefloquine for the Treatment of Uncomplicated Falciparum Malaria in Latin America and Asia

Anja Terlouw; Daniel Hayes; S. van Buuren; I. Ribeiro; Piero Olliaro; Feiko O. ter Kuile

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Anja Terlouw

Liverpool School of Tropical Medicine

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Dianne J Terlouw

Liverpool School of Tropical Medicine

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Robert Rigby

London Metropolitan University

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Feiko O. ter Kuile

Liverpool School of Tropical Medicine

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Piero Olliaro

World Health Organization

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D. Mikis Stasinopoulos

London Metropolitan University

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Eva Maria Hodel

Liverpool School of Tropical Medicine

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Ian M. Hastings

Liverpool School of Tropical Medicine

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Katherine Kay

Liverpool School of Tropical Medicine

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