Biomedical subjects

Theo Stijnen

Publications and source records attributed to Theo Stijnen.

15 recordsLinked to original sources

PubMed2003

Sensitivity and reproducibility of accelerometry and heart rate in physical strain assessment during prosthetic gait.

Accelerometry and heart rate (HR) are frequently used indicators of physical strain during normal daily life. The present study focused on the sensitivity and reproducibility of accelerometry (body motility, the intensity of body movement measured with accelerometry) and HR (percentage maximal heart rate reserve, %HRR(max)) in the assessment of physical strain during walking in persons with a lower leg amputation, using persons without an amputation as reference. Ten patients with an amputation of the leg and ten comparison subjects performed, at an interval of 1 month, the same walking protocol three times. Subjects walked at a preferred speed and at fixed speeds. At their preferred walking speed, speed (0.63 vs 1.31 m s(-1), P=0.001), body motility [0.53 vs 0.91 (arbitrary unit), P=0.001] and %HRR(max) (42.5 vs 27.6, P=0.02) differed between the amputation group and the comparison group. At fixed walking speeds, only %HRR(max) differed between groups ( P</=0.002) and showed a session effect ( P=0.02). The relationship between body motility and %HRR(max) in the patient group was significantly different from that in the comparison group. It can be concluded that accelerometry is strongly related with walking speed, but not sensitive to differences and changes in economy, contrary to %HRR(max). The use of accelerometry as an indicator of the level of physical strain in persons with an amputation is not feasible. The added value of a calibration procedure has to be studied.

Acceleration↗

PubMed2003

Thiazide diuretics and the risk for hip fracture.

BACKGROUND: Since most hip fractures are related to osteoporosis, treating accelerated bone loss can be an important strategy to prevent hip fractures. Thiazides have been associated with reduced age-related bone loss by decreasing urinary calcium excretion. OBJECTIVE: To examine the association between dose and duration of thiazide diuretic use and the risk for hip fracture and to study the consequences of discontinuing use. DESIGN: Prospective population-based cohort study. SETTING: The Rotterdam Study. PARTICIPANTS: 7891 individuals 55 years of age and older. MEASUREMENTS: Hip fractures were reported by the general practitioners and verified by trained research assistants. Details of all dispensed drugs were available on a day-to-day basis. Exposure to thiazides was divided into 7 mutually exclusive categories: never use, current use for 1 to 42 days, current use for 43 to 365 days, current use for more than 365 days, discontinuation of use since 1 to 60 days, discontinuation of use since 61 to 120 days, and discontinuation of use since more than 120 days. RESULTS: 281 hip fractures occurred. Relative to nonuse, current use of thiazides for more than 365 days was statistically significantly associated with a lower risk for hip fracture (hazard ratio, 0.46 [95% CI, 0.21 to 0.96]). There was no clear dose dependency. This lower risk disappeared approximately 4 months after thiazide use was discontinued. CONCLUSIONS: Thiazide diuretics protect against hip fracture, but this protective effect disappears within 4 months after use is discontinued.

Age Factors↗

PubMed2003

Combining multiple outcome measures in a meta-analysis: an application.

In meta-analysis of clinical trials published in the medical literature it is customary to restrict oneself to standard univariate fixed or random effects models. If multiple endpoints are present, each endpoint is analysed separately. A few articles have been written in the statistical literature on multivariate methods for multiple outcome measures. However, these methods were not easy to apply in practice, because self-written programs had to be used, and the examples were only two-dimensional. In this paper we consider a meta-analysis on the effect on stroke-free survival of surgery compared to conservative treatment in patients with increased risk of stroke. Three summary measures per trial are available: short-term post-operative morbidity/mortality in the surgical group; long-term event rate in the surgical group, and the event rate in the conservative group. We analyse the three outcomes jointly with a general linear MIXED model, compare the results with the standard univariate approaches and discuss the many advantages of multivariate modelling. It turns out that the general linear MIXED model is a very convenient framework for multivariate meta-analysis. All analyses could be carried out in standard general linear MIXED model software.

Disease-Free Survival↗

PubMed2003

Endogenous estradiol and risk of dementia in women and men: the Rotterdam Study.

We determined whether higher endogenous estradiol levels were associated with lower risk of dementia in older men and women not using hormonal replacement therapy, using a case-cohort design within the Rotterdam Study, a population-based follow-up study on chronic diseases, including dementia, in 7983 subjects aged 55 years or older, and ongoing since 1990. The analyses were based on a random subcohort of 508 women and 438 men, and on 76 women and 53 men with incident dementia. Cox proportional hazards models with robustly estimated standard errors showed that in women higher levels of total estradiol were associated with higher risk of dementia (age-adjusted hazard ratio per standard deviation increase 1.38; 95% CI 1.04-1.84). Age-adjusted HR's of Alzheimer's disease and vascular dementia associated with higher levels of total estradiol (per SD increase) were 1.24 (95% CI 0.87-1.76) and 2.19 (95% CI 1.22-3.92), respectively. Similar results were observed for bioavailable estradiol. Additional adjustments for potential confounders did not change the results substantially. In men, no clear association was observed between estradiol levels and risk of dementia or its subtypes. The findings do not support the hypothesis that higher levels of endogenous estradiol reduce risk of dementia, neither in women nor in men.

Aged↗

PubMed2003

Dialectical behaviour therapy for women with borderline personality disorder: 12-month, randomised clinical trial in The Netherlands.

BACKGROUND: Dialectical behaviour therapy (DBT) is widely considered to be a promising treatment for borderline personality disorder (BPD). However, the evidence for its efficacy published thus far should be regarded as preliminary. AIMS: To compare the effectiveness of DBT with treatment as usual for patients with BPD and to examine the impact of baseline severity on effectiveness. METHOD: Fifty-eight women with BPD were randomly assigned to either 12 months of DBT or usual treatment in a randomised controlled study. Participants were recruited through clinical referrals from both addiction treatment and psychiatric services. Outcome measures included treatment retention and the course of suicidal, self-mutilating and self-damaging impulsive behaviours. RESULTS: Dialectical behaviour therapy resulted in better retention rates and greater reductions of self-mutilating and self-damaging impulsive behaviours compared with usual treatment, especially among those with a history of frequent self-mutilation. CONCLUSIONS: Dialectical behaviour therapy is superior to usual treatment in reducing high-risk behaviours in patients with BPD.

Adult↗

PubMed2003

Final height in girls with turner syndrome after long-term growth hormone treatment in three dosages and low dose estrogens.

Although GH treatment for short stature in Turner syndrome is an accepted treatment in many countries, which GH dosage to use and which age to start puberty induction are issues of debate. This study shows final height (FH) in 60 girls with Turner syndrome treated in a randomized dose-response trial, combining GH treatment with low dose estrogens at a relatively young age. Girls were randomly assigned to group A (4 IU/m(2).d; approximately 0.045 mg/kg/d), group B (first year, 4 IU/m(2).d; thereafter 6 IU/m(2).d), or group C (first year, 4 IU/m(2).d; second year, 6 IU/m(2).d; thereafter, 8 IU/m(2).d). After a minimum of 4 yr of GH treatment, at a mean age of 12.7 +/- 0.7 yr, low dose micronized 17beta-estradiol was given orally. After a mean duration of GH treatment of 8.6 +/- 1.9 yr, FH was reached at a mean age of 15.8 +/- 0.9 yr. FH, expressed in centimeters or SD score, was 157.6 +/- 6.5 or -1.6 +/- 1.0 in group A, 162.9 +/- 6.1 or -0.7 +/- 1.0 in group B, and 163.6 +/- 6.0 or -0.6 +/- 1.0 in group C. The difference in FH in centimeters, corrected for height SD score and age at start of treatment, was significant between groups A and B [regression coefficient, 4.1; 95% confidence interval (CI), 1.4, 6.9; P < 0.01], and groups A and C (coefficient, 5.0; 95% CI, 2.3, 7.7; P < 0.001), but not between groups B and C (coefficient, 0.9; 95% CI, -1.8, 3.6). Fifty of the 60 girls (83%) had reached a normal FH (FH SD score, more than -2). After starting estrogen treatment, the decrease in height velocity (HV) changed significantly to a stable HV, without affecting bone maturation (change in bone age/change in chronological age). The following variables contributed significantly to predicting FH SD score: GH dose, height SD score (ref. normal girls), chronological age at start of treatment, and HV in the first year of GH treatment. GH treatment was well tolerated. In conclusion, GH treatment leads to a normalization of FH in most girls, even when puberty is induced at a normal pubertal age. The optimal GH dosage depends on height and age at the start of treatment and first year HV.

Body Height↗

PubMed2003

Validation and calibration of the Kabi Pharmacia International Growth Study prediction model for children with idiopathic growth hormone deficiency.

In 1999 a model was published for prediction of growth in children with idiopathic GH deficiency (IGHD) during GH therapy, derived using data from the Kabi Pharmacia International Growth Study (KIGS) database (Pharmacia \|[amp ]\| Upjohn, Inc., International Growth Database). We validated and calibrated this KIGS model for growth in the first year of GH therapy using data from 136 Dutch children with IGHD. Observed vs. predicted outcomes were plotted, and the fitted regression line was significantly different from the line of identity (P = 0.03). It appeared that the predictions were too extreme: relatively low predictions were too low, relatively high predictions were too high. This is a well known phenomenon in the context of prediction models, called overoptimism. For valid application to other data the KIGS predictions should be calibrated. Calibrated predictions are obtained using Y(cal) = Y(orig) + (2.153 - 0.192 x Y(orig)), where Y(cal) is the calibrated prediction, and Y(orig) is the KIGS prediction. The calibrated prediction will be higher than the original KIGS prediction when the original prediction is less than 11.2 cm/yr and will be lower otherwise. The variability of the prediction errors of the calibrated predictions was positively related to the value of the prediction (P < 0.001), described by the equation SD(pred err) = -1.017 + 0.286 x Y(cal). Our calibrated model will give better predictions for children with IGHD fulfilling the same criteria.

Calibration↗

PubMed2002

Favourable mutation test outcomes for individuals at risk for Huntington disease change the perspectives of first-degree relatives.

In mutation testing for Huntington disease, an autosomal dominant hereditary late-onset disorder, unfavourable test outcomes in at-risk individuals provide important information about other family members at risk. On the other hand, common counselling practice considers favourable outcomes as non-informative for at-risk relatives, except for the offspring of the tested individual. We shall show, however, that favourable outcomes also change the perspectives for the tested individual's first-degree relatives at risk. In the case of a (prospective) parent originally at 50% risk, and with n equalling the number of children or fetuses identified as non-carriers, the probability of being a non-carrier equals 2 (n)/(2 (n)+1) for the at-risk parent, providing that none of the offspring of this parent has been identified as a carrier. Likewise, the probability of being a non-carrier equals (2 (n+1)+1)/(2 (n+1)+2) for the (future) siblings of the tested individual. These changes in probabilities are important for individuals who are considering prenatal or presymptomatic DNA-testing for autosomal dominant hereditary late-onset disorders, such as Huntington disease and hereditary forms of cancer (BRCA1/2, FAP, HNPCC). Consequences can be far reaching in the case of pregnancies, where the risk of miscarriage after a prenatal test is 1%-2%. Parents initially at 50% risk may consider not having a prenatal test in successive pregnancies, knowing that favourable test results in previous pregnancies have considerably reduced their personal risk.

DNA Mutational Analysis↗

PubMed2002

Using correspondence analysis in pharmacy practice.

Correspondence analysis (CA) and some of its uses in pharmacy practice are described. CA is a multivariate and graphic form of exploratory data analysis that reduces a multidimensional contingency table to a two-dimensional plot with minimal loss of information. An exploratory association between medication use and the number and severity of falls among the elderly living at home is used to illustrate the process of CA. Row profiles are constructed by dividing the count data in each cell by the total of the corresponding row, converting frequency data into relative frequencies. A graph of the data can be made by recalculating the frequencies to illustrate how the data might appear in a three-dimensional space with the axes defined by the three categories of falling (minimum, moderate, and major). For example, the number of patients using central nervous system (CNS) agents is plotted using the relative frequencies as vectors to locate a position in the three-dimensional space. All drug profiles and the average profile will lie exactly in a triangular plane defined by the terminal points of each axis. In this manner, data with three dimensions can be projected onto a two-dimensional space. Transferring the vectors named by pharmacologic class onto the plot requires creating two axes that cross at a common point or the origin. This point locates the average profile and defines an important reference for making comparisons. CA revealed that CNS agents may be associated with moderate to major falls, psychotherapeutic agents with moderate falls, and anticoagulants with moderate to minimum falls. CA has widespread uses in pharmacy practice. It can identify patients at risk for serious but preventable drug-related complications, enabling pharmacists to allocate pharmacy resources to the areas in most need and suggest hypotheses for future research. Clinicians can also use CA to analyze vast amounts of patient-related data to uncover hard-to-detect associations. The use of CA in pharmacy practice will allow new strategies for improved patient care to be more readily appreciated and implemented.

Accidental Falls↗

PubMed2002

Advanced methods in meta-analysis: multivariate approach and meta-regression.

This tutorial on advanced statistical methods for meta-analysis can be seen as a sequel to the recent Tutorial in Biostatistics on meta-analysis by Normand, which focused on elementary methods. Within the framework of the general linear mixed model using approximate likelihood, we discuss methods to analyse univariate as well as bivariate treatment effects in meta-analyses as well as meta-regression methods. Several extensions of the models are discussed, like exact likelihood, non-normal mixtures and multiple endpoints. We end with a discussion about the use of Bayesian methods in meta-analysis. All methods are illustrated by a meta-analysis concerning the efficacy of BCG vaccine against tuberculosis. All analyses that use approximate likelihood can be carried out by standard software. We demonstrate how the models can be fitted using SAS Proc Mixed.

BCG Vaccine↗

PubMed2002

Reliability of sacroiliac joint laxity measurement with Doppler imaging of vibrations.

We developed a noninvasive technique, referred to as Doppler imaging of vibrations (DIV), to measure laxity of the sacroiliac joint (SIJ). The purpose of this study was to examine the reliability of SIJ laxity measurements. A total of 10 healthy women (mean 29.6 +/- 6 years old) participated in the study. At both sides, SIJ laxity was measured with DIV in threshold units (TU). Reliability and measurement error were assessed from repeated measurements by five testers on two occasions as well as by one experienced tester. Intraclass correlation coefficients ranged from 0.53 to 0.80 for all five testers, and from 0.75 to 0.89 for the one experienced tester. Only changes larger than 1.94 to 3.60 TU (any tester) or 1.45 to 2.38 TU (experienced tester) could be confidently detected. DIV is a reliable technique for SIJ laxity measurements in healthy subjects, when performed by an experienced tester.

Adult↗

PubMed2002

Hypertension is frequently present in patients with reflux esophagitis or Barrett's esophagus but not in those with non-ulcer dyspepsia.

BACKGROUND: Elevated mortality due to cardiovascular disease has been reported for patients with Barrett's esophagus (BE). We compared the prevalence of risk factors for cardiovascular disease in patients with BE, reflux esophagitis (RE), and non-ulcer dyspepsia (NUD) with that of the general population. METHODS: Patients with upper gastrointestinal complaints and BE, RE, or NUD were compared with a matched cohort from the general population using a questionnaire and blood pressure and cholesterol measurements. RESULTS: Hypertension occurred more frequently in patients with BE (odds ratio 5.1, P<0.0001) and RE (odds ratio 3.8, P<0.001), but not in those with NUD. Serum total cholesterol was higher in BE (P=0.02) and borderline in RE (P=0.06) but not in NUD. Mean HDL cholesterol levels, body mass index, and smoking did not differ. CONCLUSIONS: This study suggests that BE and RE found at diagnostic endoscopy are associated with an increased prevalence of hypertension and a higher total cholesterol level than in the general population. If so, this would explain the increased mortality during the follow-up of BE patients, and it should be taken into account when designing or evaluating follow-up studies of BE.

Journal Article↗

PubMed2002

Three-dimensional US assessment of hepatic volume, head circumference, and abdominal circumference in healthy and growth-restricted fetuses.

PURPOSE: To establish reproducibility and normal values for fetal hepatic volume and its significance in identification of fetal growth restriction relative to head and upper abdominal circumferences according to a cross-sectional study design. MATERIALS AND METHODS: Pregnant women (n = 135) underwent ultrasonography. The coefficient of variation (CV) for hepatic volume scans obtained at 0 and 20 minutes and hepatic area tracings, performed twice for each scan, was determined (n = 20; range, 23-36 weeks). Normal data for hepatic volume and head and upper abdominal circumferences were obtained (n = 85; range, 20-36 weeks) and related to data from growth-restricted fetuses (birth weight < P5 centile; n = 24; range, 22-36 weeks). RESULTS: CV was 2.9% for volume scans and 1.6% for area tracings. In 85 uncomplicated cases, mean fetal hepatic volume (P50 centile) was 9.7 mL +/- 4.4 (SD) at 20 weeks and 96.4 mL +/- 8.2 at 36 weeks of gestation. In 24 growth-restricted fetuses, hepatic volume, head circumference, and upper abdominal circumference expressed as percentages of the normal P50 centile were 45%, 90%, and 82%, respectively. Mean difference in hepatic volume between fetal growth restriction and normal fetal development, as expressed with the z score, -4.32 +/- 1.4, was significantly different (P <.05) from that for head circumference, -3.04 +/- 1.3, but not from that for upper abdominal circumference, -4.7 +/- 1.2. Fetal hepatic measurement was obtained in 109 pregnancies. CONCLUSION: Acceptable reproducibility exists for hepatic volume determinations. In fetal growth restriction, reduction is more pronounced for hepatic volume than for head or upper abdominal circumference; hepatic volume is a better discriminator than head circumference but not upper abdominal circumference.

Abdomen↗

PubMed2002

Effect of discontinuation of long-term growth hormone treatment on carbohydrate metabolism and risk factors for cardiovascular disease in girls with Turner syndrome.

GH treatment increases insulin levels in girls with Turner syndrome (TS), who are already predisposed to develop diabetes mellitus and other risk factors for developing cardiovascular disease. Therefore, in the present study, we investigated carbohydrate metabolism and several other risk factors that may predict development of cardiovascular disease in girls with TS after discontinuation of long-term GH treatment. Fifty-six girls, participating in a randomized dose-response study, were examined before, during, and 6 months after discontinuing long-term GH treatment with doses of 4 IU/m(2).d ( approximately 0.045 mg/kg.d), 6 IU/m(2).d, or 8 IU/m(2).d. After a minimum of 4 yr of GH treatment, low-dose micronized 17beta-estradiol was given orally. Mean (SD) age at 6 months after discontinuation of GH treatment was 15.8 (0.9) yr. Mean duration of GH treatment was 8.8 (1.7) yr. Six months after discontinuation of GH treatment, fasting glucose levels decreased and returned to pretreatment levels. The area under the curve for glucose decreased to levels even lower than pretreatment level (P < 0.001). Fasting insulin levels and the area under the curve for insulin decreased to levels just above pretreatment level (P < 0.001 for both), although being not significantly different from the control group. No dose-dependent differences among GH dosage groups were found. At 6 months after discontinuation, impaired glucose tolerance was present in 1 of 53 girls (2%), and none of the girls developed diabetes mellitus type 1 or 2. Compared with pretreatment, the body mass index SD-score had increased (P < 0.001), and the systolic and diastolic blood pressure SD-score had decreased significantly at 6 months after discontinuation of GH treatment (P < 0.001 for both) although remaining above zero (P < 0.001, P < 0.05, and P < 0.005, respectively). Compared with pretreatment, total cholesterol (TC) did not change after discontinuation of GH treatment, whereas the atherogenic index [AI = TC/high-density lipoprotein cholesterol (TC/HDL-c)] and low-density lipoprotein cholesterol (LDL-c) had decreased; and both HDL-c and triglyceride levels increased (P < 0.001 for AI, LDL-c, and HDL-c; P < 0.05 for triglyceride). Compared with the control group, AI, serum TC, and LDL-c levels were significantly lower (P < 0.001 for all), whereas HDL-c levels were significantly higher (P < 0.05). In conclusion, after discontinuation of long-term GH treatment in girls with TS, the GH-induced insulin resistance disappeared, blood pressure decreased but remained higher than in the normal population, and lipid levels and the AI changed to more cardio-protective values.

Blood Pressure↗

PubMedDate not supplied

Prolonged use of proton pump inhibitors, CagA status, and the outcome of Helicobacter pylori gastritis.

GOALS AND BACKGROUND: To assess whether prolonged use of proton pump inhibitors (PPIs) in patients infected with Helicobacter pylori has adverse effects on gastritis. STUDY: We studied 34 H. pylori-positive individuals with reflux esophagitis, Barrett esophagus, or nonulcer dyspepsia. Half of them were on maintenance treatment with PPIs (mean, 8 years) and half were not.H. pylori and CagA status were tested serologically. Gastric biopsies were classified histopathologically by the updated Sydney classification. RESULTS: Proton pump inhibitors in H. pylori gastritis are associated with significantly less antral inflammation and lower H. pylori density, regardless of CagA status. There was a tendency toward more antral atrophy in patients with the CagA strain who were undergoing maintenance treatment with PPIs (p = 0.08), but there was an opposite tendency in CagA-negative individuals (p = 0.08). Intestinal metaplasia was seen more frequently in CagA-positive, treated individuals (p = 0.028). CONCLUSIONS: These findings support the hypothesis that CagA status is important in the progression to atrophy and that maintenance treatment with PPIs accelerate this progression, while reducing inflammatory infiltration.

Anti-Ulcer Agents↗