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Biomedical subjects

N J D Nagelkerke

Publications and source records attributed to N J D Nagelkerke.

At least 19 recordsLinked to original sources
PubMed2006

Completeness of notification of tuberculosis in The Netherlands: how reliable is record-linkage and capture-recapture analysis?

The aim of this study was to describe a systematic process of record-linkage, cross-validation, case-ascertainment and capture-recapture analysis to assess the quality of tuberculosis registers and to estimate the completeness of notification of incident tuberculosis cases in The Netherlands in 1998. After record-linkage and cross-validation 1499 tuberculosis patients were identified, of whom 1298 were notified, resulting in an observed under-notification of 13.4%. After adjustment for possible imperfect record-linkage and remaining false-positive hospital cases observed under-notification was 7.3%. Log-linear capture-recapture analysis initially estimated a total number of 2053 (95% CI 1871-2443) tuberculosis cases, resulting in an estimated under-notification of 36.8%. After adjustment for possible imperfect record-linkage and remaining false-positive hospital cases various capture-recapture models estimated under-notification at 13.6%. One of the reasons for the higher than expected estimated under-notification in a country with a well-organized system of tuberculosis control might be that some tuberculosis cases, e.g. extrapulmonary tuberculosis, are managed by clinicians less familiar with notification of infectious diseases. This study demonstrates the possible impact of violation of assumptions underlying capture-recapture analysis, especially the perfect record-linkage, perfect positive predictive value and absent three-way interaction assumptions.

Disease Notification↗
PubMed2006

Preventing nosocomial infections: improving compliance with standard precautions in an Indonesian teaching hospital.

Standard precautions can prevent transmission of micro-organisms. This study investigated hand hygiene, handling of needles and use of personal protective equipment in an Indonesian teaching hospital, and performed a multi-faceted intervention study to improve compliance. An intervention was performed in an internal medicine ward and a paediatric ward, consisting of development of a protocol for standard precautions, installation of washstands, educational activities and performance feedback. Before, during and after the intervention, observers monitored compliance with hand hygiene, safe handling of needles and use of gloves, gowns and masks. A gynaecology ward served as the control. Unobtrusive observations were performed to check for an influence of the observers on the overt observations. In total, 7,160 activities were observed. Compliance with hand hygiene increased from 46% to 77% in the internal medicine ward and from 22% to 62% in the paediatric ward. Before the intervention, no safe recapping of needles was recorded in either ward. After the intervention, 20% of needles were recapped safely. Inappropriate gown use decreased in the internal medicine ward. There were no significant changes in use of gloves and masks. There may have been an effect of the overt observations in the paediatric ward, but there was no effect in the internal medicine ward. There were no significant changes in the control ward, except for a decrease in the use of gloves. In conclusion, compliance with hand hygiene procedures improved significantly due to an intervention project focused on education and improved facilities. Compliance with safe handling of needles improved slightly due to introduction of the one-handed method for safe recapping of used needles.

Cross Infection↗
PubMed2006

Early life circumstances and atopic disorders in childhood.

The prevalence of childhood atopic disorders has risen dramatically in the last decades of the past century. Risk factors for the development of these disorders have been studied extensively. This review focuses on the role of early life risk factors such as pre-natal development, perinatal circumstances, birth order and childhood vaccinations.

Birth Order↗
PubMed2006

Inter- and intra-individual variation in applied force when listening at a surface, and resulting variation in earprints.

We aimed to explore the level of inter- and intra-individual variation in applied force when listening at a surface, and assess the resulting variation in earprints. We further intended to identify possible sources of this variation. Forty subjects each listened twenty-four times at a surface while applied force was recorded. In between efforts the level and frequency of the target sound, and the level of ambient noise were varied. Each listening effort was characterized by two values: the mean of a series of force recordings ('functional force') and the highest force reading of the effort ('peak value'). A mixed model analysis of variance revealed that repetition during multiple efforts of listening and the level of the target sound significantly affected both values for applied force. The frequency of the target sound affected the peak value, but we assume this was due to confounding effects. The level of ambient noise did not affect applied force. To explore the correlation between values for applied force of various efforts by single ear, the intra-class correlation coefficient was calculated. For functional force it was 0.80; for the peak value it was 0.79. To study intra-individual variation in earprints, five prints from each ear were lifted and studied. Variation in prints is discussed.

Analysis of Variance↗
PubMed2005

Surveillance of healthcare-associated infections in Indonesian hospitals.

A cross-sectional surveillance of healthcare-associated infections (HAIs) and exposure to risk factors was undertaken in two Indonesian teaching hospitals (Hospitals A and B). Patients from internal medicine, surgery, obstetrics and gynaecology, paediatrics, a class department and intensive care were included. Patient demographics, antibiotic use, culture results, presence of HAI [phlebitis, surgical site infection (SSI), urinary tract infection (UTI) and septicaemia] and risk factors were recorded. To check for interobserver variation, a validation study was performed in Hospital B. In Hospitals A and B, 1,334 and 888 patients were included, respectively. Exposure to invasive devices and surgery was 59%. In Hospital A, 2.8% of all patients had phlebitis, 1.7% had SSI, 0.9% had UTI and 0.8% had septicaemia. In Hospital B, 3.8% had phlebitis, 1.8% had SSI, 1.1% had UTI and 0.8% had septicaemia. In the validation study, the prevalence as recorded by the first team was 2.6% phlebitis, 1.8% SSI, 0.9% UTI and no septicaemia, and that recorded by the second team was 2.2% phlebitis, 2.6% SSI, 3.5% UTI and 0.9% septicaemia. This study is the first to report on HAI in Indonesia. Prevalence rates are comparable to those in other countries. The reliability of the surveillance was insufficient as a considerable difference in prevalence rates was found in the validation study. The surveillance method used is a feasible tool for hospitals in countries with limited healthcare resources to estimate their level of HAI and make improvements in infection control. Efficiency can be improved by restricting the surveillance to include only those patients with invasive procedures. This can help to detect 90% of all infections while screening only 60% of patients.

Adolescent↗
PubMed2005

Estimation of minimum infection rates with Legionella pneumophila in an exposed population.

The distribution of antibody levels to Legionella (L.) pneumophila (serotypes 1-7) was compared between subjects who worked near the source of a large outbreak of Legionnaires' disease (n=668) and a population sample of comparable age (n=480). In a previous analysis of these data, it was estimated that 80% of those working near the source were infected with L. pneumophila. However, the estimation procedure implicitly assumes that the probability of infection does not depend on the antibody level of a person before exposure. This is questionable, as antibodies could protect against infection. We have now estimated the minimum value consistent with the data on the number of infected persons. We observed that a minimum of 40% [95% confidence interval (CI) 32-48] of those working near the source and 13% (95% CI 8-18) of those working further away were infected with L. pneumophila. Implications of these findings for design options in future research are discussed.

Adolescent↗
PubMed2005

Study of the relationship between a person's stature and the height of an ear imprint from the floor.

Occasionally ear prints are found at crime scenes. The height of the ear imprint may provide the police with information regarding the stature of the perpetrator and may therefore help to narrow down the number of suspects. The research provides calculations for the determination of stature from the height of the tragus imprint found at crime scenes. It takes into account various variables such as age, stature and gender.

Adult↗
PubMed2005

Can viral load, semi-quantitatively evaluated, of human papillomavirus predict cytological or histological outcome in women with atypical squamous or glandular cells of undetermined significance cytology?

OBJECTIVE: 1) To assess the regression to normal cytology in women with cervical smears diagnosed as atypical squamous or glandular cells of undetermined significance (ASCUS/AGUS) and absence or clearance of human papillomavirus (HPV) infection; 2) To evaluate the association between viral load, semi-quantitatively evaluated, and cytological or histological outcome. MATERIAL AND METHODS: In this cohort study HPV test and biopsy was taken in 148 women with ASCUS/AGUS cytology. After 12-18 months a HPV test and cervical smear were repeated in 121 women. RESULTS: Absence or clearance of HPV showed significantly more regression to normal cytology than persistent or newly acquired infected women, odds ratio 27 (95% confidence interval; 7-103). The viral load of the HPV test at enrollment was not correlated with the follow-up cytological outcome (Spearman correlation coefficient 0.2, p = 0.2). A marked association between viral load and histological outcome at enrollment was shown (Spearman correlation coefficient 0.43, p < 0.0001). CONCLUSION: Absence or clearance of HPV can predict regression to normal cytology. Viral load at enrollment cannot predict cytological regression. There was a marked association between viral load and the underlying CIN at enrollment. However, there was large overlapping of viral loads among the grades of CIN. Therefore, viral load is not a useful parameter to predict high-grade lesions in women with ASCUS/AGUS cytology.

Adolescent↗
PubMed2004

Risk factors for the presence of Campylobacter spp. in Dutch broiler flocks.

The campylobacter status of 495 broiler flocks sampled in The Netherlands between April 1997 and December 2000 was related to farm- and flock-specific information obtained from questionnaires to identify potential risk factors for campylobacter presence. Approximately 30% of the flocks tested positive for Campylobacter spp. in at least one pooled faecal sample. Multivariable logistic regression showed significant risk increments for: ages 29-35 days (OR = 2.34) and 36-42 days (OR = 3.96) compared to 22-28 days; > or =5 broiler houses on the premises (OR = 3.02); the presence of other farm animals on the farm (OR = 1.88); the presence of animals on farms within 1 km (OR = 9.56); and summer (OR = 3.48) and fall (OR = 2.59) compared to winter. Furthermore, hatcheries differed (ORs from 5.42 to 20.2), although this variable showed strong collinearity with the variables explaining feed mill and integrated poultry operations. We also identified interaction in which an increased risk from children entering the broiler house (OR = 28.0) was diminished by the use of broiler-specific workclothes. Population attributable fractions (PAFs) suggested that animals on farms within 1 km (PAF = 0.76) and hatchery (PAF = 0.67) had the highest impacts on campylobacter presence in Dutch broiler flocks. These factors, however, lack an easy interpretation of the mechanism behind the suggested effect.

Age Factors↗
PubMed2004

Effects of meteorological factors on epidemic malaria in Ethiopia: a statistical modelling approach based on theoretical reasoning.

This study was conducted to quantify the association between meteorological variables and incidence of Plasmodium falciparum in areas with unstable malaria transmission in Ethiopia. We used morbidity data pertaining to microscopically confirmed cases reported from 35 sites throughout Ethiopia over a period of approximately 6-7 years. A model was developed reflecting biological relationships between meteorological and morbidity variables. A model that included rainfall 2 and 3 months earlier, mean minimum temperature of the previous month and P. falciparum case incidence during the previous month was fitted to morbidity data from the various areas. The model produced similar percentages of over-estimation (19.7% of predictions exceeded twice the observed values) and under-estimation (18.6%, were less than half the observed values). Inclusion of maximum temperature did not improve the model. The model performed better in areas with relatively high or low incidence (>85% of the total variance explained) than those with moderate incidence (55-85% of the total variance explained). The study indicated that a dynamic immunity mechanism is needed in a prediction model. The potential usefulness and drawbacks of the modelling approach in studying the weather-malaria relationship are discussed, including a need for mechanisms that can adequately handle temporal variations in immunity to malaria.

Altitude↗
PubMed2004

Aircraft noise around a large international airport and its impact on general health and medication use.

AIMS: To assess the prevalence of general health status, use of sleep medication, and use of medication for cardiovascular diseases, and to study their relation to aircraft noise exposure. METHODS: These health indicators were measured by a cross-sectional survey among 11 812 respondents living within a radius of 25 km around Schiphol airport (Amsterdam). RESULTS: Adjusted odds ratios ranged from 1.02 to 2.34 per 10 dB(A) increase in L(den). The associations were statistically significant for all indicators, except for use of prescribed sleep medication or sedatives and frequent use of this medication. None of the health indicators were associated with aircraft noise exposure during the night, but use of non-prescribed sleep medication or sedatives was associated with aircraft noise exposure during the late evening (OR = 1.72). Vitality related health complaints such as tiredness and headache were associated with aircraft noise, whereas most other physical complaints were not. Odds ratios for the vitality related complaints ranged from 1.16 to 1.47 per 10 dB(A) increase in L(den). A small fraction of the prevalence of poor self rated health (0.13), medication for cardiovascular diseases or increased blood pressure (0.08), and sleep medication or sedatives (0.22) could be attributed to aircraft noise. Although the attributable fraction was highest in the governmentally noise regulated area, aircraft noise had more impact in the non-regulated area, due to the larger population. CONCLUSIONS: Results suggest associations between community exposure to aircraft noise and the health indicators poor general health status, use of sleep medication, and use of medication for cardiovascular diseases.

Adolescent↗
PubMed2003

Modeling familial clustered breast cancer using published data.

The purpose of this research was to model the familial clustering of breast cancer and to provide an accurate risk estimate for individuals from the general population, based on their family history of breast and ovarian cancer. We constructed a genetic model as an extension of a model by Claus et al. (E. B. Claus et al., Am. J. Hum. Genet., 48: 232-242, 1991), with three breast cancer genes, BRCA1, BRCA2, and a hypothetical BRCAu, in two variants, one in which BRCAu was dominant and one in which BRCAu was recessive. The model parameters were estimated using published estimates of population incidence and relative risks. Risk estimation was performed for a set of 196 counselees and for a set of simulated counselees with both the dominant BRCAu and the recessive BRCAu model, and compared relating to medical management. Estimates of the model parameters were found. Relative risks among family members were comparable between the model of Claus et al. (E. B. Claus et al., Am. J. Hum. Genet., 48: 232-242, 1991) and our model. The dominant and the recessive model provided approximately similar lifetime risks for breast cancer. Our model is suitable for breast cancer risk estimation in a health care setting.

Adult↗
PubMed2002

Differences between reference laboratories of the European community in their ability to detect Salmonella species.

The ability of national reference laboratories for Salmonella of the European Union member states to detect Salmonella bacteria was tested in four collaborative studies during the period 1995 through 1999. Three different methods were prescribed in the four studies. Capsules containing various numbers of Salmonella Typhimurium or Salmonella Enteritidis were tested. In studies II, III and IV, Salmonella bacteria were isolated in the presence of competitive microorganisms. Significant differences were found between the four studies due to varying levels of difficulty with regard to the level of contamination, the use of serotypes and the presence of competitive organisms. There were also significant differences between the laboratories in the results obtained. Possible reasons for these differences will be further investigated by the European Union Community Reference Laboratory for Salmonella.

Bacterial Typing Techniques↗
PubMed2002

Differences between national reference laboratories of the European community in their ability to serotype Salmonella species.

The capacity of national reference laboratories of the European Union member states to correctly serotype Salmonella strains was assessed in four collaborative studies on serotyping in the period 1995-1999. Participants were asked to identify 20 strains in studies I, II and III and 16 strains in study IV, using the typing method routinely performed in their laboratory. In the first study, the strains to be identified belonged to Salmonella enterica subsp. enterica, salamae or houtenae, while in the other studies only strains belonging to Salmonella enterica subsp. enterica were included. Significant differences between laboratories and between studies were found. Differences were related to the frequency of actual occurrence of the study strains in the area served by the laboratory and the number of antisera available in the laboratory.

Bacterial Typing Techniques↗
PubMed2002

Improvement of differentiation and interpretability of spoligotyping for Mycobacterium tuberculosis complex isolates by introduction of new spacer oligonucleotides.

The direct repeat (DR) region in Mycobacterium tuberculosis complex strains is composed of multiple well-conserved 36-bp DRs interspersed with nonrepetitive DNA spacer sequences of similar size. Clinical isolates show extensive polymorphism in this DR region, and this has led to the development of a 43-spacer reversed line blot methodology: spoligotyping. Although this method has contributed significantly to the molecular epidemiology of tuberculosis in the last decade, the discriminatory power and the readability of this method were not found to be optimal. In order to improve the discriminatory power, the usefulness of 43 redesigned oligonucleotides and the usefulness of 51 new spacer oligonucleotides were evaluated. For 314 M. tuberculosis complex strains isolated in the central part of The Netherlands over a 5-year period, 264 different IS6110 RFLP types could be distinguished, and 160 different spoligotype patterns were identified by traditional spoligotyping. After the introduction of 51 new spacer oligonucleotides, 14 additional spoligotypes were recognized. This enabled us to split 11 clusters of isolates identified by the traditional spoligotyping. Furthermore, on the basis of the new spacer oligonucleotides a dichotomy was found among the Beijing genotype isolates. Among 76 Mycobacterium bovis strains, 20 patterns were found by traditional spoligotyping and 30 patterns were found by novel probe spoligotyping, respectively. Nine M. bovis subsp. caprae isolates yielded six patterns by traditional spoligotyping and eight patterns by novel probe spoligotyping. A part of the redesigned oligonucleotides slightly improved the reading of spoligotype patterns. The reproducibility of spoligotyping, based on internal control probes, invariably yielded a high score; only 4 (1%) of the 314 patient isolates gave discrepant results. Analysis of a set of 31 duplicate M. tuberculosis complex strains demonstrated a 10% error rate for the identification of blinded duplicate samples. In a redundancy analysis, 40 essential spacer oligonucleotides of the 94-spacer sequences were selected, yielding the same number of spoligotype patterns. We propose to leave the traditional commercialized first-generation membrane for spoligotyping unchanged for current applications and to introduce a second-generation spoligotyping membrane whenever extended discrimination is required, e.g., for low-copy-number IS6110 strains or for phylogenetic studies of Beijing genotype strains.

Animals↗
PubMed2002

The impact of immigration on the elimination of tuberculosis in The Netherlands: a model based approach.

OBJECTIVE: To determine whether elimination of tuberculosis in the Dutch population can be achieved by the year 2030, taking into account the impact of immigration. METHODS: The incidence of tuberculosis (all forms) in the period 1970 to 2030 was estimated using a life-table model for the Dutch population without the impact of immigration. The influence of immigration on tuberculosis incidence among the Dutch was modelled using four immigrant scenarios, distinguished by the assumed contact rate between immigrants and the Dutch population, and by different projections (middle, upper) of the future size of the immigrant population in The Netherlands. RESULTS: The incidence of smear-positive tuberculosis among the Dutch is projected to be 1.4 per million in the scenario without the influence of immigrant cases, and ranging from 3.8 to 11.8 per million in the four immigrant scenarios. In all immigrant scenarios, the prevalence of tuberculosis infection will continue to decline and be less than 1% by the year 2030. At least 60% of Dutch tuberculosis cases in the year 2030 are expected to be the result of transmission from a foreign source case. CONCLUSION: Using a prevalence of tuberculosis infection of less than 1% as the elimination criterion, tuberculosis will probably be eliminated from the indigenous Dutch population by 2030. However, the incidence of smear-positive tuberculosis is expected to remain higher than 1 per million, and the majority of new tuberculosis cases among the Dutch may be attributable to recent infection from a foreign source case.

Adolescent↗
PubMed2002

Can ivermectin mass treatments eliminate onchocerciasis in Africa?

OBJECTIVE: To elucidate the conditions in which mass treatment with ivermectin reduces the transmission of Onchocerca volvulus sufficiently to eliminate infection from an African community. METHODS: ONCHOSIM, a microsimulation model for onchocerciasis transmission, was used to explore the implications of different treatment intervals, coverage levels and precontrol endemicities for the likelihood of elimination. FINDINGS: Simulations suggested that control strategies based exclusively on ivermectin mass treatments could eliminate onchocerciasis. The duration of treatment required to eliminate infection depended heavily on the treatment programme and precontrol endemicity. In areas with medium to high levels of infection, annual mass treatments with 65% coverage for at least 25 years were necessary. Model predictions suggested that durations exceeding 35 years would be required if there were much heterogeneity in exposure to vector bites and, consequently, wide individual variation in microfilaria counts. If the treatment interval were reduced from 12 to 6 months the time for completion of the programme could be more than halved and elimination could be accomplished in areas of hyperendemicity, provided that the effects of each treatment would be the same as with annual treatments. However, it was doubtful whether high coverage levels could be sustained long enough to achieve worldwide eradication. CONCLUSION: Elimination of onchocerciasis from most endemic foci in Africa appears to be possible. However, the requirements in terms of duration, coverage, and frequency of treatment may be prohibitive in highly endemic areas.

Africa↗