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author:("hops, Arno W")
2.  Clinical epidemiology of heart failure 
Heart  2007;93(9):1137-1146.
doi:10.1136/hrt.2003.025270
PMCID: PMC1955040  PMID: 17699180
4.  Added value of a physician‐and‐nurse‐directed heart failure clinic: results from the Deventer–Alkmaar heart failure study 
Heart  2006;93(7):819-825.
Aim
To determine whether an intensive intervention at a heart failure (HF) clinic by a combination of a clinician and a cardiovascular nurse, both trained in HF, reduces the incidence of hospitalisation for worsening HF and/or all‐cause mortality (primary end point) and improves functional status (including left ventricular ejection fraction, New York Heart Association (NYHA) class and quality of life) in patients with NYHA class III or IV.
Setting
Two regional teaching hospitals in The Netherlands.
Methods
240 patients were randomly allocated to the 1‐year intervention (n = 118) or usual care (n = 122). The intervention consisted of 9 scheduled patient contacts—at day 3 by telephone, and at weeks 1, 3, 5, 7 and at months 3, 6, 9 and 12 by a visit—to a combined, intensive physician‐and‐nurse‐directed HF outpatient clinic, starting within a week after hospital discharge from the hospital or referral from the outpatient clinic. Verbal and written comprehensive education, optimisation of treatment, easy access to the clinic, recommendations for exercise and rest, and advice for symptom monitoring and self‐care were provided. Usual care included outpatient visits initialised by individual cardiologists in the cardiology departments involved and applying the guidelines of the European Society of Cardiology.
Results
During the 12‐month study period, the number of admissions for worsening HF and/or all‐cause deaths in the intervention group was lower than in the control group (23 vs 47; relative risk (RR) 0.49; 95% confidence interval (CI) 0.30 to 0.81; p = 0.001). There was an improvement in left ventricular ejection fraction (LVEF) in the intervention group (plus 2.6%) compared with the usual care group (minus 3.1%; p = 0.004). Patients in the intervention group were hospitalised for a total of 359 days compared with 644 days for those in the usual care group. Beneficial effects were also observed on NYHA classification, prescription of spironolactone, maximally reached dose of β‐blockers, quality of life, self‐care behaviour and healthcare costs.
Conclusion
A heart failure clinic involving an intensive intervention by both a clinician and a cardiovascular nurse substantially reduces hospitalisations for worsening HF and/or all‐cause mortality and improves functional status, while decreasing healthcare costs, even in a country with a primary‐care‐based healthcare system.
doi:10.1136/hrt.2006.095810
PMCID: PMC1994472  PMID: 17065182
5.  Strategy to recognize and initiate treatment of chronic heart failure in primary care (STRETCH): a cluster randomized trial 
Background
Most patients with heart failure are diagnosed and managed in primary care, however, underdiagnosis and undertreatment are common. We assessed whether implementation of a diagnostic-therapeutic strategy improves functionality, health-related quality of life, and uptake of heart failure medication in primary care.
Methods/Design
A selective screening study followed by a single-blind cluster randomized trial in primary care. The study population consists of patients aged 65 years or over who presented themselves to the general practitioner in the previous 12 months with shortness of breath on exertion. Patients already known with established heart failure, confirmed by echocardiography, are excluded. Diagnostic investigations include history taking, physical examination, electrocardiography, and serum N-terminal pro B-type natriuretic peptide levels. Only participants with an abnormal electrocardiogram or an N-terminal pro B-type natriuretic peptide level exceeding the exclusionary cutpoint for non-acute onset heart failure (> 15 pmol/L (≈ 125 pg/ml)) will undergo open-access echocardiography. The diagnosis of heart failure (with reduced or preserved ejection fraction) is established by an expert panel consisting of two cardiologists and a general practitioner, according to the criteria of the European Society of Cardiology guidelines.
Patients with newly established heart failure are allocated to either the 'care as usual’ group or the 'intervention’ group. Randomization is at the level of the general practitioner. In the intervention group general practitioners receive a single half-day training in heart failure management and the use of a structured up-titration scheme. All participants fill out quality of life questionnaires at baseline and after six months of follow-up. A six-minute walking test will be performed in patients with heart failure. Information on medication and hospitalization rates is extracted from the electronic medical files of the general practitioners.
Discussion
This study will provide information on the prevalence of unrecognized heart failure in elderly with shortness of breath on exertion, and the randomized comparison will reveal whether management based on a half-day training of general practitioners in the practical application of an up-titration scheme results in improvements in functionality, health-related quality of life, and uptake of heart failure medication in heart failure patients compared to care as usual.
Trial registration
ClinicalTrials.gov NCT01202006
doi:10.1186/1471-2261-14-1
PMCID: PMC3898002  PMID: 24400643
Heart failure; Diagnosis; Treatment; Elderly; Primary care; Cluster randomized trial
6.  Drug development for exceptionally rare metabolic diseases: challenging but not impossible 
Background
We studied to what extent the level of scientific knowledge on exceptionally rare metabolic inherited diseases and their potential orphan medicinal products is associated with sponsors deciding to apply for an orphan designation at the US Food and Drug Administration (FDA) or the European Medicines Agency (EMA).
Methods
All metabolic diseases with a genetic cause and prevalence of less than 10 patients per 1 million of the population were selected from the ‘Orphanet database of Rare diseases’. The outcome of interest was the application for an orphan designation at FDA or EMA. The level of publicly available knowledge of the disease and drug candidate before an orphan designation application was defined as whether the physiological function corresponding with the pathologic gene and initiation of the pathophysiological pathway was known, whether an appropriate animal study was identified for the disease, whether preclinical proof of concept was ascertained and the availability of data in humans. Other determinants included in the study were metabolic disease class, the prevalence of the disease, prognosis and time of first description of the disease in the literature. Univariate relative risks (RRs) and 95% confidence intervals (CIs) of an orphan designation application were calculated for each of these determinants. In addition, a multivariate Cox regression analysis was conducted (Forward LR).
Results
In total, 166 rare metabolic genetic diseases were identified and included in the analysis. For only 42 (25%) of the diseases an orphan designation application was submitted at either FDA or EMA before January 2012. The multivariate analysis identified preclinical proof of concept of a potential medicinal product as major knowledge related determinant associated with an orphan designation application (RRadj 3.9, 95% CI 1.9-8.3) and confirmed that prevalence of the disease is also associated with filing an application for an orphan designation (RRadj 2.8, 95% CI 1.4-5.4).
Conclusion
For only one out of four known exceptionally rare metabolic inherited diseases sponsors applied for an orphan designation at FDA or EMA. These applications were found to be associated with the prevalence of the rare disease and the level of available scientific knowledge on the proof of concept linking possible drug candidates to the disease of interest.
doi:10.1186/1750-1172-8-179
PMCID: PMC3843583  PMID: 24237580
Rare disease; Orphan medicinal product; Inherited metabolic disease; Prevalence; Preclinical proof of concept
7.  Use of Expert Panels to Define the Reference Standard in Diagnostic Research: A Systematic Review of Published Methods and Reporting 
PLoS Medicine  2013;10(10):e1001531.
Loes C. M. Bertens and colleagues survey the published diagnostic research literature for use of expert panels to define the reference standard, characterize components and missing information, and recommend elements that should be reported in diagnostic studies.
Please see later in the article for the Editors' Summary
Background
In diagnostic studies, a single and error-free test that can be used as the reference (gold) standard often does not exist. One solution is the use of panel diagnosis, i.e., a group of experts who assess the results from multiple tests to reach a final diagnosis in each patient. Although panel diagnosis, also known as consensus or expert diagnosis, is frequently used as the reference standard, guidance on preferred methodology is lacking. The aim of this study is to provide an overview of methods used in panel diagnoses and to provide initial guidance on the use and reporting of panel diagnosis as reference standard.
Methods and Findings
PubMed was systematically searched for diagnostic studies applying a panel diagnosis as reference standard published up to May 31, 2012. We included diagnostic studies in which the final diagnosis was made by two or more persons based on results from multiple tests. General study characteristics and details of panel methodology were extracted. Eighty-one studies were included, of which most reported on psychiatry (37%) and cardiovascular (21%) diseases. Data extraction was hampered by incomplete reporting; one or more pieces of critical information about panel reference standard methodology was missing in 83% of studies. In most studies (75%), the panel consisted of three or fewer members. Panel members were blinded to the results of the index test results in 31% of studies. Reproducibility of the decision process was assessed in 17 (21%) studies. Reported details on panel constitution, information for diagnosis and methods of decision making varied considerably between studies.
Conclusions
Methods of panel diagnosis varied substantially across studies and many aspects of the procedure were either unclear or not reported. On the basis of our review, we identified areas for improvement and developed a checklist and flow chart for initial guidance for researchers conducting and reporting of studies involving panel diagnosis.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Before any disease or condition can be treated, a correct diagnosis of the condition has to be made. Faced with a patient with medical problems and no diagnosis, a doctor will ask the patient about their symptoms and medical history and generally will examine the patient. On the basis of this questioning and examination, the clinician will form an initial impression of the possible conditions the patient may have, usually with a most likely diagnosis in mind. To support or reject the most likely diagnosis and to exclude the other possible diagnoses, the clinician will then order a series of tests and diagnostic procedures. These may include laboratory tests (such as the measurement of blood sugar levels), imaging procedures (such as an MRI scan), or functional tests (such as spirometry, which tests lung function). Finally, the clinician will use all the data s/he has collected to reach a firm diagnosis and will recommend a program of treatment or observation for the patient.
Why Was This Study Done?
Researchers are continually looking for new, improved diagnostic tests and multivariable diagnostic models—combinations of tests and characteristics that point to a diagnosis. Diagnostic research, which assesses the accuracy of new tests and models, requires that each patient involved in a diagnostic study has a final correct diagnosis. Unfortunately, for most conditions, there is no single, error-free test that can be used as the reference (gold) standard for diagnosis. If an imperfect reference standard is used, errors in the final disease classification may bias the results of the diagnostic study and may lead to a new test being adopted that is actually less accurate than existing tests. One widely used solution to the lack of a reference standard is “panel diagnosis” in which two or more experts assess the results from multiple tests to reach a final diagnosis for each patient in a diagnostic study. However, there is currently no formal guidance available on the conduct and reporting of panel diagnosis. Here, the researchers undertake a systematic review (a study that uses predefined criteria to identify research on a given topic) to provide an overview of the methodology and reporting of panel diagnosis.
What Did the Researchers Do and Find?
The researchers identified 81 published diagnostic studies that used panel diagnosis as a reference standard. 37% of these studies reported on psychiatric diseases, 21% reported on cardiovascular diseases, and 12% reported on respiratory diseases. Most of the studies (64%) were designed to assess the accuracy of one or more diagnostic test. Notably, one or more critical piece of information on methodology was missing in 83% of the studies. Specifically, information on the constitution of the panel was missing in a quarter of the studies and information on the decision-making process (whether, for example, a diagnosis was reached by discussion among panel members or by combining individual panel member's assessments) was incomplete in more than two-thirds of the studies. In three-quarters of the studies for which information was available, the panel consisted of only two or three members; different fields of expertise were represented in the panels in nearly two-thirds of the studies. In a third of the studies for which information was available, panel members made their diagnoses without access to the results of the test being assessed. Finally, the reproducibility of the decision-making process was assessed in a fifth of the studies.
What Do These Findings Mean?
These findings indicate that the methodology of panel diagnosis varies substantially among diagnostic studies and that reporting of this methodology is often unclear or absent. Both the methodology and reporting of panel diagnosis could, therefore, be improved substantially. Based on their findings, the researchers provide a checklist and flow chart to help guide the conduct and reporting of studies involving panel diagnosis. For example, they suggest that, when designing a study that uses panel diagnosis as the reference standard, the number and background of panel members should be considered, and they provide a list of options that should be considered when planning the decision-making process. Although more research into each of the options identified by the researchers is needed, their recommendations provide a starting point for the development of formal guidelines on the methodology and reporting of panel diagnosis for use as a reference standard in diagnostic research.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001531.
Wikipedia has a page on medical diagnosis (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
The Equator Network is an international initiative that seeks to improve the reliability and value of medical research literature by promoting transparent and accurate reporting of research studies; its website includes information on a wide range of reporting guidelines, including the STAndards for the Reporting of Diagnostic accuracy studies (STARD), an initiative that aims to improve the accuracy and completeness of reporting of studies of diagnostic accuracy
doi:10.1371/journal.pmed.1001531
PMCID: PMC3797139  PMID: 24143138
8.  Development and validation of a model to predict the risk of exacerbations in chronic obstructive pulmonary disease 
Purpose
Prediction models for exacerbations in patients with chronic obstructive pulmonary disease (COPD) are scarce. Our aim was to develop and validate a new model to predict exacerbations in patients with COPD.
Patients and methods
The derivation cohort consisted of patients aged 65 years or over, with a COPD diagnosis, who were followed up over 24 months. The external validation cohort consisted of another cohort of COPD patients, aged 50 years or over. Exacerbations of COPD were defined as symptomatic deterioration requiring pulsed oral steroid use or hospitalization. Logistic regression analysis including backward selection and shrinkage were used to develop the final model and to adjust for overfitting. The adjusted regression coefficients were applied in the validation cohort to assess calibration of the predictions and calculate changes in discrimination applying C-statistics.
Results
The derivation and validation cohort consisted of 240 and 793 patients with COPD, of whom 29% and 28%, respectively, experienced an exacerbation during follow-up. The final model included four easily assessable variables: exacerbations in the previous year, pack years of smoking, level of obstruction, and history of vascular disease, with a C-statistic of 0.75 (95% confidence interval [CI]: 0.69–0.82). Predictions were well calibrated in the validation cohort, with a small loss in discrimination potential (C-statistic 0.66 [95% CI 0.61–0.71]).
Conclusion
Our newly developed prediction model can help clinicians to predict the risk of future exacerbations in individual patients with COPD, including those with mild disease.
doi:10.2147/COPD.S49609
PMCID: PMC3797610  PMID: 24143086
exacerbation of COPD; risk prediction; external validation; vascular disease
9.  Regulatory Scientific Advice on Non-Inferiority Drug Trials 
PLoS ONE  2013;8(9):e74818.
The active-controlled trial with a non-inferiority design has gained popularity in recent years. However, non-inferiority trials present some methodological challenges, especially in determining the non-inferiority margin. Regulatory guidelines provide some general statements on how a non-inferiority trial should be conducted. Moreover, in a scientific advice procedure, regulators give companies the opportunity to discuss critical trial issues prior to the start of the trial. The aim of this study was to identify potential issues that may benefit from more explicit guidance by regulators. To achieve this, we collected and analyzed questions about non-inferiority trials posed by applicants for scientific advice in Europe in 2008 and 2009, as well as the responses given by the European Medicines Agency (EMA). In our analysis we included 156 final letters of advice from 2008 and 2009, addressed to 94 different applicants (manufacturers). Our analysis yielded two major findings: (1) applicants frequently asked questions ‘whether’ and ‘how’ to conduct a non-inferiority trial, 26% and 74%, respectively, and (2) the EMA regulators seem mainly concerned about the choice of the non-inferiority margin in non-inferiority trials (36% of total regulatory answers). In 40% of the answers, the EMA recommended using a stricter margin, and in 10% of the answers regarding non-inferiority margins, the EMA questioned the justification of the proposed non-inferiority margin.
We conclude that there are still difficulties in selecting the appropriate methodology for non-inferiority trials. Straightforward and harmonized guidance regarding non-inferiority trials is required, for example on whether it is necessary to conduct such a trial and how the non-inferiority margin is determined. It is unlikely that regulatory guidelines can cover all therapeutic areas; therefore, in some cases regulatory scientific advice may be used as an opportunity for tailored advice.
doi:10.1371/journal.pone.0074818
PMCID: PMC3764030  PMID: 24040346
10.  β-Blockers and All-Cause Mortality in Adults with Episodes of Acute Bronchitis: An Observational Study 
PLoS ONE  2013;8(6):e67122.
Background
Recent observational studies suggest that β-blockers may improve long-term prognosis in patients with chronic obstructive pulmonary disease (COPD). We assessed whether β-blocker use improves all-cause mortality in patients with episodes of acute bronchitis.
Methods
An observational cohort study using data from the electronic medical records of 23 general practices in the Netherlands. The data included standardized information about daily patient contacts, diagnoses, and drug prescriptions. Cox regression was applied with time-varying treatment and covariates.
Results
The study included 4,493 patients aged 45 years and older, with at least one episode of acute bronchitis between 1996 and 2006. The mean (SD) age of the patients was 66.9 (11.7) years, and 41.9% were male. During a mean (SD) follow up period of 7.7 (2.5) years, 20.4% developed COPD. In total, 22.7% had cardiovascular comorbidities, resulting in significant higher mortality rates than those without (51.7% vs. 12.0%, p<0.001). The adjusted hazard ratio of cardioselective β-blocker use for mortality was 0.62 (95% confidence interval [CI], 0.50–0.77), and 1.01 (95% CI 0.75–1.36) for non-selective ones. Some other cardiovascular drugs also reduced the risk of mortality, with adjusted HRs of 0.60 (95% CI 0.46–0.79) for calcium channel blockers, 0.88 (95% CI 0.73–1.06) for ACE inhibitors/angiotensin receptor blockers, and 0.42 (95% CI 0.31–0.57) for statins, respectively.
Conclusion
Cardiovascular comorbidities are common and increase the risk of mortality in adults with episodes of acute bronchitis. Cardioselective β-blockers, but also calcium channel blockers and statins may reduce mortality, possibly as a result of cardiovascular protective properties.
doi:10.1371/journal.pone.0067122
PMCID: PMC3686763  PMID: 23840599
11.  Serum extracellular vesicle protein levels are associated with acute coronary syndrome 
Aims:
Biomarkers are essential in the early detection of acute coronary syndromes (ACS). Serum extracellular vesicles are small vesicles in the plasma containing protein and RNA and have been shown to be involved in ACS-related processes like apoptosis and coagulation. Therefore, we hypothesized that serum extracellular vesicle protein levels are associated with ACS.
Methods and results:
Three serum extracellular vesicle proteins potentially associated with ACS were identified with differential Q-proteomics and were evaluated in 471 frozen serum samples of ACS-suspected patients presenting to the emergency department (30% of whom had an ACS). Protein levels were measured after vesicle isolation using ExoQuick. Mean serum extracellular vesicle concentration of the different proteins was compared between ACS and non-ACS patients. Selected proteins were tested in a univariate logistic regression model, as well as in a multivariate model to adjust for cardiovascular risk factors. A separate analysis was performed in men and women. In the multivariate logistic regression analysis, polygenic immunoglobulin receptor, (pIgR; OR 1.630, p=0.026), cystatin C (OR 1.641, p=0.021), and complement factor C5a (C5a, OR 1.495, p=0.025) were significantly associated with ACS, while total vesicle protein concentration was borderline significant. The association of the individual proteins with ACS was markedly stronger in men.
Conclusions:
These data show that serum extracellular vesicle pIgR, cystatin C, and C5a concentrations are independently associated with ACS and that there are pronounced gender differences. These observations should be validated in a large, prospective study to assess the potential role of vesicle content in the evaluation of patients suspected of having an ACS.
doi:10.1177/2048872612471212
PMCID: PMC3760575  PMID: 24062934
ACS; acute coronary syndrome; biomarker; extracellular vesicle; protein
13.  Early assessment of acute coronary syndromes in the emergency department: the potential diagnostic value of circulating microRNAs 
EMBO Molecular Medicine  2012;4(11):1176-1185.
Previous studies investigating the role of circulating microRNAs in acute coronary syndrome (ACS) were based on small patient numbers, performed no comparison with established markers of cardiac injury and did not have appropriate controls. We determined the potential diagnostic value of circulating microRNAs as novel early biomarkers in 332 suspected ACS patients on presentation to the emergency department (ED) in a prospective single-centre study including cardiac miRNAs (miR-1, -208a and -499), miR-21 and miR-146a. Levels of all miRs studied were significantly increased in 106 patients diagnosed with ACS, even in patients with initially negative high-sensitive (hs) troponin or symptom onset <3 h. MiR-1, miR-499 and miR-21 significantly increased the diagnostic value in all suspected ACS patients when added to hs-troponin T (AUC 0.90). These three miRs were strong predictors of ACS independent of clinical co-variates including patient history and cardiovascular risk factors. Interestingly, the combination of these three miRs resulted in a significantly higher AUC of 0.94 than hs-troponin T (0.89). Circulating microRNAs hold great potential as novel early biomarkers for the management of suspected ACS patients.
doi:10.1002/emmm.201201749
PMCID: PMC3494874  PMID: 23023917
acute coronary syndrome; circulating microRNA; miR-1; miR-21; miR-499
15.  Triage of frail elderly with reduced exercise tolerance in primary care (TREE). a clustered randomized diagnostic study 
BMC Public Health  2012;12:385.
Background
Exercise reduced tolerance and breathlessness are common in the elderly and can result in substantial loss in functionality and health related quality of life. Heart failure (HF) and chronic obstructive pulmonary disease (COPD) are common underlying causes, but can be difficult to disentangle due to overlap in symptomatology. In addition, other potential causes such as obesity, anaemia, renal dysfunction and thyroid disorders may be involved.
We aim to assess whether screening of frail elderly with reduced exercise tolerance leads to high detection rates of HF, COPD, or alternative diagnoses, and whether detection of these diseases would result in changes in patient management and increase in both functionality and quality of life.
Methods/Design
A cluster randomized diagnostic trial. Primary care practices are randomized to the diagnostic-treatment strategy (screening) or care as usual.
Patient population: Frail (defined as having three or more chronic or vitality threatening diseases and/or receiving five or more drugs chronically during the last year) community-dwelling persons aged 65 years and older selected from the electronic medical files of the participating general practitioners. Those with reduced exercise tolerance or moderate to severe dyspnoea (≥2 score on the Medical Research Counsel dyspnoea scale) are included in the study.
The diagnostic screening in the intervention group includes history taking, physical examination, electrocardiography, spirometry, blood tests, and echocardiography. Subsequently, participants with new diagnoses will be managed according to clinical guidelines. Participants in the control arm receive care as usual. All participants fill out health status and other relevant questionnaires at baseline and after 6 months of follow-up.
Discussion
This study will generate information on the yield of screening for previously unrecognized HF, COPD and other chronic diseases in frail elderly with reduced exercise tolerance and/or exercise induced dyspnoea. The cluster randomized comparison will reveal whether this yield will result in subsequent improvements in functional health and/or health related quality of life.
Trial registration
ClinicalTrials.gov NCT01148719
doi:10.1186/1471-2458-12-385
PMCID: PMC3407748  PMID: 22640176
Reduced exercise tolerance; Dyspnoea; Breathlessness; Heart failure; COPD; Frail; Elderly; Screening
17.  Selection of confounding variables should not be based on observed associations with exposure 
European Journal of Epidemiology  2011;26(8):589-593.
In observational studies, selection of confounding variables for adjustment is often based on observed baseline incomparability. The aim of this study was to evaluate this selection strategy. We used clinical data on the effects of inhaled long-acting beta-agonist (LABA) use on the risk of mortality among patients with obstructive pulmonary disease to illustrate the impact of selection of confounding variables for adjustment based on baseline comparisons. Among 2,394 asthma and COPD patients included in the analyses, the LABA ever-users were considerably older than never-users, but cardiovascular co-morbidity was equally prevalent (19.9% vs. 19.9%). Adjustment for cardiovascular co-morbidity status did not affect the crude risk ratio (RR) for mortality: crude RR 1.19 (95% CI 0.93–1.51) versus RR 1.19 (95% CI 0.94–1.50) after adjustment for cardiovascular co-morbidity. However, after adjustment for age (RR 0.95, 95% CI 0.76–1.19), additional adjustment for cardiovascular co-morbidity status did affect the association between LABA use and mortality (RR 1.01, 95% CI 0.80–1.26). Confounding variables should not be discarded based on balanced distributions among exposure groups, because residual confounding due to the omission of confounding variables from the adjustment model can be relevant.
doi:10.1007/s10654-011-9606-1
PMCID: PMC3168755  PMID: 21796419
Bias; Confounder selection; Confounding; Pharmacoepidemiology
18.  Undetected chronic obstructive pulmonary disease and asthma in people over 50 years with persistent cough 
Background
Chronic obstructive pulmonary disease (COPD) and asthma are underdiagnosed in primary care.
Aim
To determine how often COPD or asthma are present in middle-aged and older patients who consult their GP for persistent cough.
Design of study
A cross-sectional study in 353 patients older than 50 years, visiting their GP for persistent cough and not known to have COPD or asthma.
Setting
General practice in the Netherlands.
Method
All participants underwent extensive diagnostic work-up, including symptoms, signs, spirometry, and body plethysmography. All results were studied by an expert panel to diagnose or exclude COPD and/or asthma. The reproducibility of the panel diagnosis was assessed by calculation of Cohen's κ statistic in a sample of 41 participants.
Results
Of the 353 participants, 102 (29%, 95% confidence interval [CI] = 24 to 34%) were diagnosed with COPD. In 14 of these 102 participants, both COPD and asthma were diagnosed (4%, 95% CI = 2 to 7%). Asthma (without COPD) was diagnosed in 23 (7%, 95% CI = 4 to 10%) participants. Mean duration of cough was 93 days (median 40 days). The reproducibility of the expert panel was good (Cohen's κ = 0.90).
Conclusion
In patients aged over 50 years who consult their GP for persistent cough, undetected COPD or asthma is frequently present.
doi:10.3399/bjgp10X514738
PMCID: PMC2894377  PMID: 20594438
asthma; cough; COPD; early diagnosis
19.  Regulatory scientific advice in drug development: does company size make a difference? 
Purpose
To assess whether the content of Scientific Advice (SA) questions addressed to a national drug regulatory agency is associated with company size. This may help to increase understanding about the knowledge, strategic, and regulatory gaps companies face during drug development.
Methodology
A cross-sectional analysis was performed of SA provided by the Dutch Medicines Evaluation Board (MEB) in 2006–2008. Definition of company size was based on ranking by total revenues (Scrip’s Pharmaceutical Company League Tables 2008). The content of each SA question was scored according to predefined domains (quality, nonclinical, clinical, regulatory, and product information), their subdomains (e.g., efficacy), and a selection of additional content variables (e.g., endpoints, choice of active comparator).
Results
In total, 201 SA documents including 1,087 questions could be identified. Small, medium-sized, and large companies asked for SA 110 (54.7%), 40 (19.9%), and 51 (25.4%) times, respectively. Clinical questions were asked most often (65.9%), mainly including efficacy (33.2%) and safety questions (24.0%). The most frequent topics were overall efficacy and safety strategy. Small companies asked quality and nonclinical questions more often (P < 0.001) and clinical questions less frequently than large companies (P = 0.004). Small companies asked significantly more clinical questions about pharmacokinetics, including bioequivalence, than medium-sized and large companies (P < 0.001).
Conclusion
The array of topics addressed in SA provides an interesting outlook on what industry considers to be still unresolved in drug development and worthwhile to discuss with regulators. Company size is associated with the content of SA questions. MEB advice accommodates both innovative and noninnovative drug development.
doi:10.1007/s00228-010-0919-x
PMCID: PMC3021701  PMID: 21049297
Drug development; Scientific Advice; Company size
20.  Room for Improvement in Conducting and Reporting Non-Inferiority Randomized Controlled Trials on Drugs: A Systematic Review 
PLoS ONE  2010;5(10):e13550.
Background
A non-inferiority (NI) trial is intended to show that the effect of a new treatment is not worse than the comparator. We conducted a review to identify how NI trials were conducted and reported, and whether the standard requirements from the guidelines were followed.
Methodology and Principal Findings
From 300 randomly selected articles on NI trials registered in PubMed at 5 February 2009, we included 227 NI articles that referred to 232 trials. We excluded studies on bioequivalence, trials on healthy volunteers, non-drug trials, and articles of which the full-text version could not be retrieved. A large proportion of trials (34.0%) did not use blinding. The NI margin was reported in 97.8% of the trials, but only 45.7% of the trials reported the method to determine the margin. Most of the trials used either intention to treat (ITT) (34.9%) or per-protocol (PP) analysis (19.4%), while 41.8% of the trials used both methods. Less than 10% of the trials included a placebo arm to confirm the efficacy of the new drug and active comparator against placebo, and less than 5.0% were reporting the similarity of the current trial with the previous comparator's trials. In general, no difference was seen in the quality of reporting before and after the release of the CONSORT statement extension 2006 or between the high-impact and low-impact journals.
Conclusion
The conduct and reporting of NI trials can be improved, particularly in terms of maximizing the use of blinding, the use of both ITT and PP analysis, reporting the similarity with the previous comparator's trials to guarantee a valid constancy assumption, and most importantly reporting the method to determine the NI margin.
doi:10.1371/journal.pone.0013550
PMCID: PMC2965079  PMID: 21048948
21.  Advantages of the nested case-control design in diagnostic research 
Background
Despite its benefits, it is uncommon to apply the nested case-control design in diagnostic research. We aim to show advantages of this design for diagnostic accuracy studies.
Methods
We used data from a full cross-sectional diagnostic study comprising a cohort of 1295 consecutive patients who were selected on their suspicion of having deep vein thrombosis (DVT). We draw nested case-control samples from the full study population with case:control ratios of 1:1, 1:2, 1:3 and 1:4 (per ratio 100 samples were taken). We calculated diagnostic accuracy estimates for two tests that are used to detect DVT in clinical practice.
Results
Estimates of diagnostic accuracy in the nested case-control samples were very similar to those in the full study population. For example, for each case:control ratio, the positive predictive value of the D-dimer test was 0.30 in the full study population and 0.30 in the nested case-control samples (median of the 100 samples). As expected, variability of the estimates decreased with increasing sample size.
Conclusion
Our findings support the view that the nested case-control study is a valid and efficient design for diagnostic studies and should also be (re)appraised in current guidelines on diagnostic accuracy research.
doi:10.1186/1471-2288-8-48
PMCID: PMC2500041  PMID: 18644127
22.  Quality of life in smokers: focus on functional limitations rather than on lung function? 
Background
The Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification of severity of chronic obstructive pulmonary disease (COPD) is based solely on obstruction and does not capture physical functioning. The hypothesis that the Medical Research Council (MRC) dyspnoea scale would correlate better with quality of life than the level of airflow limitation was examined.
Aim
To study the associations between quality of life in smokers and limitations in physical functioning (MRC dyspnoea scale) and, quality of life and airflow limitation (GOLD COPD stages).
Design
Cross-sectional study.
Setting
The city of IJsselstein, a small town in the centre of The Netherlands.
Method
Male smokers aged 40–65 years without a prior diagnosis of COPD and enlisted with a general practice, participated in this study. Quality of life was assessed by means of a generic (SF–36) and a disease-specific, questionnaire (QOLRIQ).
Results
A total of 395 subjects (mean age 55.4 years, pack years 27.1) performed adequate spirometry and completed the questionnaires. Limitations of physical functioning according to the MRC dyspnoea scale were found in 25.1 % (99/395) of the participants and airflow limitation in 40.2% (159/395). The correlations of limitations of physical functioning with all quality-of-life components were stronger than the correlations of all quality-of-life subscales with the severity of airflow limitation.
Conclusion
In middle-aged smokers the correlation of limitations of physical functioning (MRC dyspnoea scale) with quality of life was stronger than the correlation of the severity of airflow limitation with quality of life. Future staging systems of severity of COPD should capture this and not rely on forced expiratory volume in one second (FEV1) alone.
PMCID: PMC2078172  PMID: 17550673
dyspnoea; FEV1; middle-aged; FEV1; quality of life; smokers
23.  Effectiveness and costs of implementation strategies to reduce acid suppressive drug prescriptions: a systematic review 
Background
Evaluation of evidence for the effectiveness of implementation strategies aimed at reducing prescriptions for the use of acid suppressive drugs (ASD).
Methods
A systematic review of intervention studies with a design according to research quality criteria and outcomes related to the effect of reduction of ASD medication retrieved from Medline, Embase and the Cochrane Library. Outcome measures were the strategy of intervention, quality of methodology and results of treatment to differences of ASD prescriptions and costs.
Results
The intervention varied from a single passive method to multiple active interactions with GPs. Reports of study quality had shortcomings on subjects of data-analysis. Not all outcomes were calculated but if so rction of prescriptions varied from 8% up to 40% and the cost effectiveness was in some cases negative and in others positive. Few studies demonstrated good effects from the interventions to reduce ASD.
Conclusion
Poor quality of some studies is limiting the evidence for effective interventions. Also it is difficult to compare cost-effectiveness between studies. However, RCT studies demonstrate that active interventions are required to reduce ASD volume. Larger multi-intervention studies are necessary to evaluate the most successful intervention instruments.
doi:10.1186/1472-6963-7-177
PMCID: PMC2204001  PMID: 17983477
24.  Deep vein thrombosis in primary care: possible malignancy? 
Background
The increased prevalence of unrecognised malignancy in patients with deep vein thrombosis (DVT) has been well established in secondary care settings. However, data from primary care settings, needed to tailor the diagnostic workup, are lacking.
Aim
To quantify the prevalence of unrecognised malignancy in primary care patients who have been diagnosed with DVT.
Design
Prospective follow-up study.
Setting
All primary care physicians affiliated/associated with a non-teaching hospital in a geographically circumscribed region participated in the study.
Method
A total of 430 consecutive patients without known malignancy, but with proven DVT were included in the study and compared with a control group of 442 primary care patients, matched according to age and sex. Previously unrecognised, occult malignancy was considered present if a new malignancy was diagnosed within 2 years following DVT diagnosis (DVT group) or inclusion in the control group. Patients with DVT were categorised in to those with unprovoked idiopathic DVT and those with risk factors for DVT (that is, secondary DVT).
Results
During the 2-year follow-up period, a new malignancy was diagnosed 3.6 times more often in patients with idiopathic DVT than in the control group (2-year incidence: 7.4% and 2.0%, respectively). The incidence in patients with secondary DVT was 2.6%; only slightly higher than in control patients.
Conclusion
Unrecognised malignancies are more common in both primary and secondary care patients with DVT than in the general population. In particular, patients with idiopathic DVT are at risk and they could benefit from individualised case-finding to detect malignancy.
PMCID: PMC1876636  PMID: 16954002
deep vein thrombosis; idiopathic; neoplasms; primary health care
25.  Incidence and determinants of moderate COPD (GOLD II) in male smokers aged 40–65 years: 5-year follow up 
Background
Chronic obstructive pulmonary disease (COPD) is a major health problem with an estimated prevalence of 10–15% among smokers. The incidence of moderate COPD, as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD), is largely unknown.
Aim
To determine the cumulative incidence of moderate COPD (forced expiratory volume in 1 second/forced vital capacity ratio [FEV1/FVC] <0.7 and FEV1 <80% predicted) and its association with patient characteristics in a cohort of male smokers.
Design
Prospective cohort study.
Setting
The city of IJsselstein, a small town in the Netherlands.
Method
Smokers aged 40–65 years who were registered with local GPs, participated in a study to identify undetected COPD. Baseline measurements were taken in 1998 of 399 smokers with normal spirometry (n = 292) or mild COPD (FEV1/FVC <0.7 and FEV1 ≥80% predicted, n = 107) and follow-up measurements were conducted in 2003.
Results
After a mean follow-up of 5.2 years, 33 participants developed moderate COPD (GOLD II). This showed an estimated cumulative incidence of 8.3% (95% CI = 5.8 to 11.4) and a mean annual incidence of 1.6%. No participant developed severe airflow obstruction. The risk of developing moderate COPD in smokers with baseline mild COPD (GOLD I) was five times higher than in those with baseline normal spirometry (one in five versus one in 25).
Conclusions
In a cohort of middle-aged male smokers, the estimated cumulative incidence of moderate COPD (GOLD II) over 5 years was relatively high (8.3%). Age, childhood smoking, cough, and one or more GP contacts for lower respiratory tract problems were independently associated with incident moderate COPD.
PMCID: PMC1876630  PMID: 16953996
incidence; middle-age; moderate COPD; patient characteristics; smokers

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