Biomedical subjects

Stef van Buuren

Publications and source records attributed to Stef van Buuren.

8 recordsLinked to original sources

PubMed2007

Computerized adaptive testing for measuring development of young children.

Developmental indicators that are used for routine measurement in The Netherlands are usually chosen to optimally identify delayed children. Measurements on the majority of children without problems are therefore quite imprecise. This study explores the use of computerized adaptive testing (CAT) to monitor the development of young children. CAT is expected to improve the measurement precision of the instrument. We do two simulation studies - one with real data and one with simulated data - to evaluate the usefulness of CAT. It is shown that CAT selects developmental indicators that maximally match the individual child, so that all children can be measured to the same precision.

Child Development↗

PubMed2006

Reference chart for relative weight change to detect hypernatraemic dehydration.

OBJECTIVE: The validity of the rule of thumb that infants may have a weight loss of 10% in the first days after birth is unknown. We assessed the validity of this and other rules to detect breast-fed infants with hypernatraemic dehydration. DESIGN: A reference chart for relative weight change was constructed by the LMS method. The reference group was obtained by a retrospective cohort study. PARTICIPANTS: 1544 healthy, exclusively breast-fed infants with 3075 weight measurements born in the Netherlands and 83 cases of breast-fed infants with hypernatraemic dehydration obtained from literature. RESULTS: The rule of thumb had a sensitivity of 90.4%, a specificity of 98.3% and a positive predictive value of 3.7%. Referring infants if their weight change is below -2.5 SDS (0.6th centile) in the reference chart in the first week of life and using the rule of thumb in the second week had a sensitivity of 85.5%, a specificity of 99.4% and a positive predictive value of 9.2%. CONCLUSIONS: The rule of thumb is likely to produce too many false positive results, assuming that for screening purposes the specificity needs to be high. A chart for relative weight change can be helpful to detect infants with hypernatraemic dehydration.

Breast Feeding↗

PubMed2006

An interval scale for development of children aged 0-2 years.

Measurement of development is often less precise than that of height and weight. Developmental scores are typically based on passing one or more developmental markers, but do not have interval scale so calculating differences between scores can be nonsensical. Age-specific standardized scores are sometimes used, but fail to have a common metric that allows comparison of developmental scores across age. The goal of this study is to develop a quantitative developmental score (D-score) with improved measurement characteristics. The basic assumption of the D-score is the existence of a common continuous scale for the development. Scores of 2151 children between 0 and 2 years on a Dutch developmental instrument were analysed. Application of the Rasch Model resulted in excellent reliability and satisfactory fit. This indicates that the new quantitative D-score succeeds in representing outcomes of the instrument on a common interval scale. Age-conditional reference values for the D-score were derived by means of the LMS method. The definition of the D-scores is not specific to age, so the D-score of a measured person can be compared to the D-score of another person of a different age. Difference scores between sessions can be used to evaluate developmental velocity on the individual level. To our knowledge this is the first developmental scale for children with such properties.

Child Development↗

PubMed2005

Are age references for waist circumference, hip circumference and waist-hip ratio in Dutch children useful in clinical practice?

UNLABELLED: The aim of this study was to present age references for waist circumference (WC), hip circumference (HC), and waist/hip ratio (WHR) in Dutch children. Cross-sectional data were obtained from 14,500 children of Dutch origin in the age range 0-21 years. National references were constructed with the LMS method. This method summarises the distribution by three smooth curves representing skewness (L curve), the median (M curve), and coefficient of variation (S curve). The correlations between body mass index-standard deviation score (BMI-SDS), the circumferences and their ratio, and demographic variables were assessed by (multiple) regression analysis for three age groups: 0-<5 years (1), 5-<12.5 years (2), and 12.5-<21 years (3). A cut-off for clinical use was suggested based on the International Obesity Task Force criteria for BMI. Mean WC and HC values increased with age. Mean WC was slightly higher in boys than in girls, and this difference was statistically significant from 11 years of age onwards. In contrast, HC was significantly higher in girls than in boys from 9 years onwards. The correlation between WC-SDS and BMI-SDS ( r =0.73, P <0.01) and between HC and BMI-SDS ( r =0.67, P <0.01) increased with age. With regard to WHR-SDS, a low correlation was found for 12.5-20 years of age ( r =0.2, P <0.01). WC-SDS correlated positively with height SDS ( r =0.35, P <0.01). CONCLUSION: Waist circumferences can be used to screen for increased abdominal fat mass in children, whereby a cut-off point of 1.3 standard deviation score seems most suitable.

Adolescent↗

PubMed2004

Malnutrition in critically ill children: from admission to 6 months after discharge.

BACKGROUND & AIMS: Little is known about the nutritional status of critically ill children during hospitalisation in and after discharge from an intensive care unit. We set up a prospective, observational study to evaluate the nutritional status of children in an intensive care unit from admission up to 6 months after discharge. A secondary aim was identifying patient characteristics that influence the course of the various anthropometric parameters. METHODS: The nutritional status of 293 children--104 preterm neonates, 96 term neonates and 93 older children--admitted to our multidisciplinary tertiary pediatric and neonatal intensive care unit was evaluated by anthropometry upon and during admission, at discharge and 6 weeks and 6 months following discharge. RESULTS: Upon admission, 24% of all children appeared to be undernourished. Preterm and term neonates, but not older children, showed a decline in nutritional status during admission. At 6 months after discharge almost all children showed complete recovery of nutritional status. Length of stay and history of disease were the parameters that most adversely affected the nutritional status of preterm and term neonates at discharge and during follow-up. CONCLUSION: While malnutrition is a major problem in pediatric intensive care units, most children have good long-term outcome in terms of nutritional status after discharge.

Adolescent↗

PubMed2003

Height, weight, body mass index and pubertal development reference values for children of Turkish origin in the Netherlands.

UNLABELLED: The aim of this study was to provide growth and sexual maturation reference data for Turkish children living in The Netherlands. We also compared these references with the reference data of children of Dutch origin and with Turkish reference data collected in Turkey and elsewhere in Europe. Cross-sectional growth and demographic data were collected from 2,904 children of Turkish origin and 14,500 children of Dutch origin living in the Netherlands in the age range 0-20 years. Growth references for length, height, weight for height, body mass index (BMI) and head circumference were constructed with the LMS method. Reference curves for sexual maturation and menarche were estimated by a generalised additive model. Predictive variables for height and BMI were assessed by univariate and multivariate regression analyses. Young Turkish adults were 10 cm shorter than their Dutch contemporaries. Mean height was 174.0 cm for males and 160.7 cm for females. Height differences in comparison with Dutch children started at 3 years. Height SDS was predominantly associated with target height. The height of Turkish children living in the Netherlands was similar to Turkish children in Germany and to children from high socio-economic classes in Istanbul. Compared to Dutch children, maturation stages started 0.5-0.7 years later for both sexes. In girls, median age at menarche was 12.8 years, 5 months earlier than in Dutch girls. BMI of Turkish children was higher than that of Dutch children at all ages. BMI SDS was associated with birth weight and the duration of stay of the mother in the Netherlands. CONCLUSION: Turkish children are considerably shorter and more overweight than Dutch children. Separate growth charts for Turkish children in The Netherlands are useful for growth monitoring.

Adolescent↗

PubMed2002

On the assessment of adverse drug reactions from spontaneous reporting systems: the influence of under-reporting on odds ratios.

A well-known problem in spontaneous reporting systems (SRSs) for adverse drug reactions (ADRs) is under-reporting, that is, the problem that not all occurrences of ADRs are reported to the SRS. We look at the question of how to draw statistical conclusions from analyses of SRS data using reporting odds ratios. We will show that certain under-reporting problems play no role in assessing ADRs from SRSs: the results from the analyses turn out to be biased by some specific under-reporting problems, but not by others. SRS data can be particularly useful for the assessment of drug-drug interactions. If the assumption holds that there is an under-reporting problem for a first drug, and an under-reporting problem for a second drug, but that these two under-reporting problems do not influence each other, then reporting odds ratios estimated from SRSs are useful for signalling drug-drug interactions in the ADR-experiencing population. Similar results hold for covariate-drug interactions. We illustrate our results using two examples.

Adverse Drug Reaction Reporting Systems↗

PubMedDate not supplied

Toward targeted hypertension screening guidelines.

BACKGROUND: Guidelines for screening and subsequent treatment of hypertension vary widely between countries. Part of this variation can be attributed to systematic differences between populations, but little is known about the way in which guidelines should be targeted to the population of interest. Optimal guidelines should have high yield and low complexity. The goal is to fit procedures for screening and subsequent treatment of hypertension optimally to a specific population. METHODS: Simulation study on individual cardiovascular risk profiles, with drug treatment altering the 10-year cardiovascular risk. The analysis compares the consequences of various screening and treatment alternatives. The reference scenario consists of the Dutch hypertension guidelines for primary care. A representative sample of the Dutch population aged 20 years and older is taken as the target. Main outcome measures include incidence, quality-adjusted life years won, number needed to screen, and costs (prevention, morbidity, and mortality). The discount rate is 4%. RESULTS: Strict adherence to the current hypertension guidelines saves costs (i.e., the total prevention costs are less than the costs of prevented morbidity and mortality). The following changes increase its cost-effectiveness: use of lower blood pressure levels for screening and treatment, reduction of the number of screens from 5 to 3, and active call-up of high-risk patients. The adherence to guidelines has a large influence on actual cost-effectiveness achieved in practice. CONCLUSIONS: Appropriate targeting of hypertension guidelines to a population and critical appraisal of the entire screening procedure can enhance cost-effectiveness.

Adult↗