Adriaan Blommaert | University of Antwerp (original) (raw)

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Papers by Adriaan Blommaert

Journal of Antimicrobial Chemotherapy

Many European countries have engaged in awareness campaigns to decrease outpatient antibiotic use... more Many European countries have engaged in awareness campaigns to decrease outpatient antibiotic use and several measures have been proposed, e.g. the number of defined daily doses (DDDs) or packages per 1000 inhabitants per day, producing conflicting findings. Therefore, we set out to explore what measure is most appropriate. Outpatient data on each dispensed and reimbursed medicinal package in Belgium between 2002 and 2009 were aggregated at the level of the active substance in accordance with the Anatomical Therapeutic Chemical classification and expressed as the numbers of DDDs (WHO, version 2010), packages, treatments and insured individuals per 1000 inhabitants, insured individuals and patient contacts, per day, and in July-June years. Using these measures, time trends of outpatient antibiotic use were compared and explored in detail. Expressed per 1000 inhabitants per day, outpatient antibiotic use increased between 2002-03 and 2008-09 in DDDs, whereas in packages, treatments an...

Vaccine, Jan 21, 2014

Risk groups with increased vulnerability for influenza complications such as pregnant women, pers... more Risk groups with increased vulnerability for influenza complications such as pregnant women, persons with underlying illnesses as well as persons who come into contact with them, such as health care workers, are currently given priority (along with other classic target groups) to receive seasonal influenza vaccination in Belgium. We aimed to evaluate this policy from a health care payer perspective by cost-effectiveness analysis in the three specific target groups above, while accounting for effects beyond the target group. Increasing the coverage of influenza vaccination is likely to be cost-effective for pregnant women (median €6589 per quality-adjusted life-year (QALY) gained [€4073-€10,249]) and health care workers (median €24,096/QALY gained [€16,442-€36,342]), if this can be achieved without incurring additional administration costs. Assuming an additional physician's consult is charged to administer each additional vaccine dose, the cost-effectiveness of vaccinating pregn...

Vaccine, 2015

Meningitis infections are often associated with high mortality and risk of sequelae. The costs of... more Meningitis infections are often associated with high mortality and risk of sequelae. The costs of treatment and care for meningitis are a great burden on health care systems, particularly in resource-limited settings. The objective of this study is to review data on the costs of care for meningitis in low- and middle-income countries, as well as to show how results could be extrapolated to countries without sound data. We conducted a systematic review of the literature from six databases to identify studies examining the cost of care in low- and middle-income countries for all age groups with suspected, probable, or confirmed meningitis. We extracted data on treatment costs and sequelae by infectious agent and/or pathogen, where possible. Using multiple regression analysis, a relationship between hospital costs and associated determinants was investigated in order to predict costs in countries with missing data. This relationship was used to predict treatment costs for all 144 low- and middle-income countries. The methodology of conducting a systematic review, extrapolating, and setting up a standard database can be used as a tool to inform cost-effectiveness analyses in situations where cost of care data are poor. Both acute and long-term costs of meningitis could be extrapolated to countries without reliable data. Although only bacterial causes of meningitis can be vaccine-preventable, a better understanding of the treatment costs for meningitis is crucial for low- and middle-income countries to assess the cost-effectiveness of proposed interventions in their country. This cost information will be important as inputs in future cost-effectiveness studies, particularly for vaccines.

Journal of Antimicrobial Chemotherapy, 2013

Bacterial resistance to antibiotics, driven by antibiotic consumption, imposes a major threat to ... more Bacterial resistance to antibiotics, driven by antibiotic consumption, imposes a major threat to the effective treatment of bacterial infections. In addition to reducing the amount of antibiotics prescribed, avoiding broad-spectrum antibiotics could extend the lifetime of the current arsenal of antibiotic substances. Therefore, we documented prescriber and patient characteristics associated with the choice between amoxicillin and broader-spectrum alternatives (co-amoxiclav or moxifloxacin) in recent years in Belgium. Complete reimbursement claims data (2002-09) for antibiotic prescriptions in outpatient care, including patient and prescriber characteristics, were collected for both young children (1-5 years) and the adult population (30-60 years). A backwards selection procedure within generalized estimating equations retained the most relevant determinants. The age, gender and social category of the patient were found to be predictive of the extent to which amoxicillin was prescribed instead of the broader-spectrum alternatives, with female patients generally taking a higher proportion of amoxicillin than male patients. The age category of 40-44-year-old prescribers exhibited a preference for broad-spectrum antibiotics compared with both younger and older age groups. Significant interactions between the region and the prescriber's qualification (general practitioner or paediatrician) on the choice of antibiotic for children were found. Patient (age, gender and social category) and prescriber characteristics (age, gender, region and qualification) had an influence on whether amoxicillin or the alternative broad-spectrum antibiotics were prescribed. These findings should help policy makers to better target future campaigns to promote prudent prescribing of antibiotics.

Journal of Antimicrobial Chemotherapy, 2014

Objectives: Many European countries have engaged in awareness campaigns to decrease outpatient an... more Objectives: Many European countries have engaged in awareness campaigns to decrease outpatient antibiotic use and several measures have been proposed, e.g. the number of defined daily doses (DDDs) or packages per 1000 inhabitants per day, producing conflicting findings. Therefore, we set out to explore what measure is most appropriate.

Journal of Antimicrobial Chemotherapy, 2014

To identify key determinants explaining country-year variations in antibiotic use and resistance.... more To identify key determinants explaining country-year variations in antibiotic use and resistance. Ambulatory antibiotic use data [in defined daily doses per 1000 inhabitants per day (DIDs)] for 19 European countries from 1999 to 2007 were collected, along with 181 variables describing countries in terms of their agriculture, culture, demography, disease burden, education, healthcare organization and socioeconomics. After assessing data availability, overlap and relevance, multiple imputation generalized estimating equations were applied with a stepwise selection procedure to select significant determinants of global antibiotic use (expressed in DIDs), relative use of subgroups (amoxicillin and co-amoxiclav) and resistance of Escherichia coli and Streptococcus pneumoniae. Relative humidity, healthcare expenditure proportional to gross domestic product, feelings of distrust, proportion of population aged >65 years and availability of treatment guidelines were associated with higher total antibiotic use expressed in DIDs. Restrictions on marketing activities towards prescribers, population density, number of antibiotics, educational attainment and degree of atheism were associated with a lower number of total DIDs used. Relative prescribing of amoxicillin and co-amoxiclav was mainly determined by healthcare system choices [e.g. general practitioner (GP) registration and restricted marketing]. Specific antibiotic use was found to be a significant determinant of resistance for some but not all drug/organism combinations. Incentives to stimulate GP gatekeeping were associated with lower levels of resistance, and life expectancy at age 65+ and atheism were associated with more resistance. Myriad factors influence antibiotic use and resistance at the country level and an important part of these can be modified by policy choices.

Computational Statistics & Data Analysis, 2014

Penalized generalized estimating equations with Elastic Net or L2-Smoothly Clipped Absolute Devia... more Penalized generalized estimating equations with Elastic Net or L2-Smoothly Clipped Absolute Deviation penalization are proposed to simultaneously select the most important variables and estimate their effects for longitudinal Gaussian data when multicollinearity is present. The method is able to consistently select and estimate the main effects even when strong correlations are present. In addition, the potential pitfall of time-dependent covariates is clarified. Both asymptotic theory and simulation results reveal the effectiveness of penalization as a data mining tool for longitudinal data, especially when a large number of variables is present. The method is illustrated by mining for the main determinants of life expectancy in Europe.

Journal of Antimicrobial Chemotherapy

Many European countries have engaged in awareness campaigns to decrease outpatient antibiotic use... more Many European countries have engaged in awareness campaigns to decrease outpatient antibiotic use and several measures have been proposed, e.g. the number of defined daily doses (DDDs) or packages per 1000 inhabitants per day, producing conflicting findings. Therefore, we set out to explore what measure is most appropriate. Outpatient data on each dispensed and reimbursed medicinal package in Belgium between 2002 and 2009 were aggregated at the level of the active substance in accordance with the Anatomical Therapeutic Chemical classification and expressed as the numbers of DDDs (WHO, version 2010), packages, treatments and insured individuals per 1000 inhabitants, insured individuals and patient contacts, per day, and in July-June years. Using these measures, time trends of outpatient antibiotic use were compared and explored in detail. Expressed per 1000 inhabitants per day, outpatient antibiotic use increased between 2002-03 and 2008-09 in DDDs, whereas in packages, treatments an...

Vaccine, Jan 21, 2014

Risk groups with increased vulnerability for influenza complications such as pregnant women, pers... more Risk groups with increased vulnerability for influenza complications such as pregnant women, persons with underlying illnesses as well as persons who come into contact with them, such as health care workers, are currently given priority (along with other classic target groups) to receive seasonal influenza vaccination in Belgium. We aimed to evaluate this policy from a health care payer perspective by cost-effectiveness analysis in the three specific target groups above, while accounting for effects beyond the target group. Increasing the coverage of influenza vaccination is likely to be cost-effective for pregnant women (median €6589 per quality-adjusted life-year (QALY) gained [€4073-€10,249]) and health care workers (median €24,096/QALY gained [€16,442-€36,342]), if this can be achieved without incurring additional administration costs. Assuming an additional physician's consult is charged to administer each additional vaccine dose, the cost-effectiveness of vaccinating pregn...

Vaccine, 2015

Meningitis infections are often associated with high mortality and risk of sequelae. The costs of... more Meningitis infections are often associated with high mortality and risk of sequelae. The costs of treatment and care for meningitis are a great burden on health care systems, particularly in resource-limited settings. The objective of this study is to review data on the costs of care for meningitis in low- and middle-income countries, as well as to show how results could be extrapolated to countries without sound data. We conducted a systematic review of the literature from six databases to identify studies examining the cost of care in low- and middle-income countries for all age groups with suspected, probable, or confirmed meningitis. We extracted data on treatment costs and sequelae by infectious agent and/or pathogen, where possible. Using multiple regression analysis, a relationship between hospital costs and associated determinants was investigated in order to predict costs in countries with missing data. This relationship was used to predict treatment costs for all 144 low- and middle-income countries. The methodology of conducting a systematic review, extrapolating, and setting up a standard database can be used as a tool to inform cost-effectiveness analyses in situations where cost of care data are poor. Both acute and long-term costs of meningitis could be extrapolated to countries without reliable data. Although only bacterial causes of meningitis can be vaccine-preventable, a better understanding of the treatment costs for meningitis is crucial for low- and middle-income countries to assess the cost-effectiveness of proposed interventions in their country. This cost information will be important as inputs in future cost-effectiveness studies, particularly for vaccines.

Journal of Antimicrobial Chemotherapy, 2013

Bacterial resistance to antibiotics, driven by antibiotic consumption, imposes a major threat to ... more Bacterial resistance to antibiotics, driven by antibiotic consumption, imposes a major threat to the effective treatment of bacterial infections. In addition to reducing the amount of antibiotics prescribed, avoiding broad-spectrum antibiotics could extend the lifetime of the current arsenal of antibiotic substances. Therefore, we documented prescriber and patient characteristics associated with the choice between amoxicillin and broader-spectrum alternatives (co-amoxiclav or moxifloxacin) in recent years in Belgium. Complete reimbursement claims data (2002-09) for antibiotic prescriptions in outpatient care, including patient and prescriber characteristics, were collected for both young children (1-5 years) and the adult population (30-60 years). A backwards selection procedure within generalized estimating equations retained the most relevant determinants. The age, gender and social category of the patient were found to be predictive of the extent to which amoxicillin was prescribed instead of the broader-spectrum alternatives, with female patients generally taking a higher proportion of amoxicillin than male patients. The age category of 40-44-year-old prescribers exhibited a preference for broad-spectrum antibiotics compared with both younger and older age groups. Significant interactions between the region and the prescriber's qualification (general practitioner or paediatrician) on the choice of antibiotic for children were found. Patient (age, gender and social category) and prescriber characteristics (age, gender, region and qualification) had an influence on whether amoxicillin or the alternative broad-spectrum antibiotics were prescribed. These findings should help policy makers to better target future campaigns to promote prudent prescribing of antibiotics.

Journal of Antimicrobial Chemotherapy, 2014

Objectives: Many European countries have engaged in awareness campaigns to decrease outpatient an... more Objectives: Many European countries have engaged in awareness campaigns to decrease outpatient antibiotic use and several measures have been proposed, e.g. the number of defined daily doses (DDDs) or packages per 1000 inhabitants per day, producing conflicting findings. Therefore, we set out to explore what measure is most appropriate.

Journal of Antimicrobial Chemotherapy, 2014

To identify key determinants explaining country-year variations in antibiotic use and resistance.... more To identify key determinants explaining country-year variations in antibiotic use and resistance. Ambulatory antibiotic use data [in defined daily doses per 1000 inhabitants per day (DIDs)] for 19 European countries from 1999 to 2007 were collected, along with 181 variables describing countries in terms of their agriculture, culture, demography, disease burden, education, healthcare organization and socioeconomics. After assessing data availability, overlap and relevance, multiple imputation generalized estimating equations were applied with a stepwise selection procedure to select significant determinants of global antibiotic use (expressed in DIDs), relative use of subgroups (amoxicillin and co-amoxiclav) and resistance of Escherichia coli and Streptococcus pneumoniae. Relative humidity, healthcare expenditure proportional to gross domestic product, feelings of distrust, proportion of population aged >65 years and availability of treatment guidelines were associated with higher total antibiotic use expressed in DIDs. Restrictions on marketing activities towards prescribers, population density, number of antibiotics, educational attainment and degree of atheism were associated with a lower number of total DIDs used. Relative prescribing of amoxicillin and co-amoxiclav was mainly determined by healthcare system choices [e.g. general practitioner (GP) registration and restricted marketing]. Specific antibiotic use was found to be a significant determinant of resistance for some but not all drug/organism combinations. Incentives to stimulate GP gatekeeping were associated with lower levels of resistance, and life expectancy at age 65+ and atheism were associated with more resistance. Myriad factors influence antibiotic use and resistance at the country level and an important part of these can be modified by policy choices.

Computational Statistics & Data Analysis, 2014

Penalized generalized estimating equations with Elastic Net or L2-Smoothly Clipped Absolute Devia... more Penalized generalized estimating equations with Elastic Net or L2-Smoothly Clipped Absolute Deviation penalization are proposed to simultaneously select the most important variables and estimate their effects for longitudinal Gaussian data when multicollinearity is present. The method is able to consistently select and estimate the main effects even when strong correlations are present. In addition, the potential pitfall of time-dependent covariates is clarified. Both asymptotic theory and simulation results reveal the effectiveness of penalization as a data mining tool for longitudinal data, especially when a large number of variables is present. The method is illustrated by mining for the main determinants of life expectancy in Europe.