Effect of treatments on the progression of COPD: report of a workshop held in Leuven, 11-12 March 2004

Handling underlying discrete variables with bivariate mixed hidden Markov models in NONMEM

Non-linear mixed effects models typically deal with stochasticity in observed processes but models accounting for only observed processes may not be the most appropriate for all data. Hidden Markov models (HMMs) characterize the relationship between observed and hidden variables where the hidden variables can represent an underlying and unmeasurable disease status for example. Adding stochasticity to HMMs results in mixed HMMs (MHMMs) which potentially allow for the characterization of variability in unobservable processes. Further, HMMs can be extended to include more than one observation source and are then multivariate HMMs. In this work MHMMs were developed and applied in a chronic obstructive pulmonary disease example. The two hidden states included in the model were remission and exacerbation and two observation sources were considered, patient reported outcomes (PROs) and forced expiratory volume (FEV1). Estimation properties in the software NONMEM of model parameters were investigated with and without random and covariate effect parameters. The influence of including random and covariate effects of varying magnitudes on the parameters in the model was quantified and a power analysis was performed to compare the power of a single bivariate MHMM with two separate univariate MHMMs. A bivariate MHMM was developed for simulating and analysing hypothetical COPD data consisting of PRO and FEV1 measurements collected every week for 60 weeks. Parameter precision was high for all parameters with the exception of the variance of the transition rate dictating the transition from remission to exacerbation (relative root mean squared error [RRMSE] > 150%). Parameter precision was better with higher magnitudes of the transition probability parameters. A drug effect was included on the transition rate probability and the precision of the drug effect parameter improved with increasing magnitude of the parameter. The power to detect the drug effect was improved by utilizing a bivariate MHMM model over the univariate MHMM models where the number of subject required for 80% power was 25 with the bivariate MHMM model versus 63 in the univariate MHMM FEV1 model and > 100 in the univariate MHMM PRO model. The results advocates for the use of bivariate MHMM models when implementation is possible.

Screening for COPD: the gap between logic and evidence

Chronic obstructive pulmonary disease (COPD) is a common disease leading to further morbidity and significant mortality. The first step for any condition is to make the appropriate diagnosis, and spirometry barriers abound in practice around the world. It is tempting to undertake mass screening on all smokers to detect COPD. While this would pick up cases of COPD, results of studies of its effect on COPD end-points such as exacerbations, hospitalisations and mortality are disappointing. As such, aggressive case finding of COPD by screening for symptoms that patients may not themselves perceive is very important in primary care, with subsequent spirometry defining the diagnosis.We also have to separate out population screening from individual patient interactions. Performing spirometry, even on a truly asymptomatic patient, may allow earlier diagnosis and modification of risk factors such as smoking (mostly) and exacerbation risk. It also recognises patients with early disease who are at high risk of comorbidities such as cardiac illness, such that appropriate treatment strategies can be implemented. Making a diagnosis, and even the fact of worrying about such a diagnosis, can affect the motivational level of the individual patient to cease smoking; all patients should of course be counselled to stop smoking. As such, consider the individual patient in front of you for unrecognised symptoms and therefore unrecognised illness, as making a diagnosis earlier can allow the institution of care, including smoking cessation, vaccination, bronchodilators and comorbidity management.

Airway disease: similarities and differences between asthma, COPD and bronchiectasis

Airway diseases are highly prevalent worldwide; however, the prevalence of these diseases is underestimated. Although these diseases present several common characteristics, they have different clinical outcomes. The differentiation between asthma, chronic obstructive pulmonary disease and bronchiectasis in the early stage of disease is extremely important for the adoption of appropriate therapeutic measures. However, because of the high prevalence of these diseases and the common pathophysiological pathways, some patients with different diseases may present with similar symptoms. The objective of this review is to highlight the similarities and differences between these diseases in terms of the risk factors, pathophysiology, symptoms, diagnosis and treatment.

General practice counseling for patients with chronic obstructive pulmonary disease to quit smoking: impact after 1 year of two complex interventions

OBJECTIVE

To evaluate two counseling programs in general practice to help smokers with chronic obstructive pulmonary disease (COPD) to quit smoking.

METHODS

Cluster randomized controlled trial including 68 general practices (667 patients) using a randomly assigned intervention program with counseling and advice about nicotine replacement therapy (and additional bupropion-SR in one of the programs) or usual care. Usual care consisted of periodic regular check-ups and COPD information. The main outcome measure was biochemically verified point prevalence at 12 months.

RESULTS

The two intervention groups were treated as one in the analysis because they were equally effective. The intervention resulted in a significantly self-reported higher success rate (14.5%) compared to usual care (7.4%); odds ratio=2.1, 95% confidence interval=1.1-4.1. Biochemically verified quit rates were 7.5% (intervention) and 3.4% (usual care); odds ratio=2.3, 95% confidence interval=0.9-6.0.

CONCLUSION

The program doubled the cessation rates (statistically nonsignificant). Too few participants used the additional bupropion-SR to prove its effectiveness.

PRACTICE IMPLICATIONS

The protocols can be used for COPD patients in general practice, but expectations should be modest. If quitting is unsuccessful, a stepped care approach should be considered.

Validation of smoking cessation self-reported by patients with chronic obstructive pulmonary disease

PURPOSE

The present study reports on the biochemical validation of the self-reported smoking status of patients with chronic obstructive pulmonary disease (COPD). The objective is to establish the proportion of overestimation of self-reported success rates.

METHODS

A cross-sectional smoking-status validation study including 60 patients with COPD who reported that they had stopped smoking. In the analysis of urine samples, a cut-off point of 50 ng/mL of cotinine was used.

RESULTS

At the time of biochemical validation, 55 patients reported that they had quit smoking while five patients resumed smoking. Smoking status was biochemically confirmed for 43 patients (78%) and 12 patients (22%) were classified as smokers. The sensitivity of the self- report of smoking was 29% and the specificity was 100%.

CONCLUSION

Many primary care patients with COPD do not provide valid information on their smoking status, which hamper adequate therapeutic interventions. Integration of biochemical validation in daily care could overcome this problem, but may harm the doctor-patient relationship.

Structured review: evaluating the effectiveness of nurse case managers in improving health outcomes in three major chronic diseases

AIM

This paper presents the findings of a review and appraisal of the evidence for the effectiveness of nurse case management in improving health outcomes for patients living either with Diabetes, Chronic Obstructive Pulmonary Disease or Coronary Heart Disease.

BACKGROUND

Long term chronic health conditions provide some of the greatest challenges to western health care systems. In the UK, three of the most significant chronic conditions are Diabetes, Chronic Obstructive Pulmonary Disease and Coronary Heart Disease. Patients with these long term conditions are high users of health services who often receive unplanned, poorly co-ordinated, ad-hoc care in response to an exacerbation or crisis. To counter this, the nurse case manager is identified as a central aspect of improving care for these patients. However, the evidence for the effectiveness of nurse case management in improving health outcomes for the chronically ill is scarce.

DESIGN

A structured review of the literature.

METHOD

The review was undertaken focussing on studies that evaluated nurse case management with one or all of the three major long term chronic conditions. A total of 108 papers were initially reviewed and filtered to leave 75 citations that were appraised. About 18 papers were finally included in the review and subject to thematic analysis based on the health outcomes evaluated in the studies.

RESULTS

Significantly positive results were reported for nurse case management impact on five health outcomes; 'objective clinical measurements', 'quality of life and functionality', 'patient satisfaction', 'adherence to treatment' and 'self care and service use'.

RELEVANCE TO CLINICAL PRACTICE

The evidence generated in this review suggests that nurse case managers have the potential to achieve improved health outcomes for patients with long term conditions. Further research is required to support role development and create a more targeted approach to the intervention.

Differentiating chronic obstructive pulmonary disease from asthma

PURPOSE

Chronic obstructive pulmonary disease (COPD) and asthma are chronic diseases that are increasing worldwide in incidence, prevalence, and burden. The purpose of this article is to provide nurse practitioners (NPs) with the information necessary to make a differential diagnosis and to understand the different treatment approaches to these two diseases.

DATA SOURCES

Peer-reviewed journal articles, book chapters, and evidence-based Internet sources.

CONCLUSIONS

NPs who are familiar with the pathophysiology that differentiates COPD from asthma can make an appropriate diagnosis and initiate effective pharmacologic and nonpharmacologic interventions, which may lead to a reduced incidence of exacerbations.

IMPLICATIONS FOR PRACTICE

A misdiagnosis of COPD or asthma leads to inadequate management of patients and to escalating healthcare costs. An early and accurate diagnosis can help to ensure optimal and cost-effective management of patient care.

The validity of diagnostic support of an asthma/COPD service in primary care

BACKGROUND

To support GPs in diagnosing and monitoring their patients with asthma/chronic obstructive pulmonary disease (COPD), 'asthma/COPD services' have been developed. Within these services, pulmonologists perform structured diagnostic and therapeutic assessments based on the combination of written history data and spirometry.

AIM

This study determines the validity of the diagnosis and advice when assessed using only written information.

DESIGN OF STUDY

The results of the diagnostic procedures of an asthma/COPD service were compared with the results of regular office consultations by pulmonologists.

SETTING

From January until August 2004, two pulmonologists examined 80 randomly selected patients referred to an asthma/COPD service in Eindhoven, the Netherlands.

METHOD

Concordance was analysed between diagnosis and advice based on written spirometry and history data, with assessments based on live consultations with the same patients by pulmonologists.

RESULTS

The validity of the assessed diagnosis was high (Cohen's kappa = 0.82). When the diagnosis was uncertain, the advice for medical treatment scored low in validity (Cohen's kappa = 0.39). The advice for additional diagnostic examinations had a high internal validity: in half of the patients, uncertainty in diagnosis turned into a definite diagnosis of asthma/COPD, or another cause for the complaints of the patient was revealed; in the other half, the diagnosis of asthma/COPD could be rejected.

CONCLUSIONS

A structured asthma/COPD service offering diagnosis and diagnostic advice assessed from written spirometry and history data is a new and valid facility that can support the GP who faces the complicated diagnostic procedures in a progressive number of patients with asthma/COPD.

Phenotypes of chronic obstructive pulmonary disease

The current clinical classification of smoking-related lung disease fails to take into account the heterogeneity of chronic obstructive pulmonary disease (COPD). With an increased understanding of pathophysiologic variation, COPD now clearly represents a spectrum of overlapping diseases with important extrapulmonary consequences. A "phenotype" describes the outward physical manifestations of a particular disease, and compromises anything that is part of the observable structure, function or behavior of an individual. Such phenotypic distinctions in COPD include: frequent exacerbator, pulmonary cachectic, rapid decliner, airways hyperresponsiveness, impaired exercise tolerance, and emphysema versus airways disease. These variable manifestations, each with unique prognostic, clinical and physiologic ramifications, represent distinct phenotypes within COPD. While all of these phenotypes have smoking as a common risk factor, the other risk factors that determine these phenotypes remain poorly understood. An individual smoker has variable expression of each phenotype and there is mounting evidence that COPD phenotypes have different clinical outcomes. These phenotypes can be broadly classified into one of three groups: clinical, physiologic and radiographic. This review presents the evidence for the spectrum of COPD phenotypes with a focused discussion on the pathophysiologic, epidemiologic and clinical significance of each subtype.

Exacerbations and lung function decline in COPD: New insights in current and ex-smokers

AIM

To investigate whether there is a significant relationship between an increased frequency of exacerbations and the rate of forced expiratory volume in 1s (FEV(1)) decline in COPD patients. METHODS-MEASUREMENTS: About 102 COPD patients (44 smokers, 58 ex-smokers) participated in a 3-year prospective study. Exacerbations were identified as worsening of patient's respiratory symptoms as recorded on diary cards. Spirometry was performed every 6 months. The effect of frequent exacerbations on lung function was investigated using random effects models.

RESULTS

The median (mean(95% CI)) annual exacerbation rate was 2.85 (3.1 (2.7-3.6)). Patients with an annual exacerbation rate over the median rate had significantly lower baseline post-bronchodilation FEV(1)(%pred), higher MRC dyspnoea score and chronic cough compared to patients who had an annual exacerbation rate less than the median. The average annual rate of FEV(1)(%pred), adjusted for smoking decline (DeltaFEV(1)), was found significantly increased in frequent compared to infrequent exacerbators (P=0.017). The highest DeltaFEV(1) was observed in smokers frequent exacerbators and a significant interaction between exacerbation frequency and DeltaFEV(1) was also observed in ex-smokers.

CONCLUSIONS

Our findings suggest that an increased frequency of exacerbations is significantly associated with FEV(1) decline even in ex-smokers. Thus, smoking and frequent exacerbations may have both negative impact on lung function. Smoking cessation and prevention of exacerbations should be a major target in COPD.

Association of Hck genetic polymorphisms with gene expression and COPD

Polymorphonuclear leukocytes (PMNs) are major effector cells in the chronic airway inflammation in chronic obstructive pulmonary disease (COPD). PMN degranulation is associated with degradation of extracellular matrix and tissue damage. Hck is an essential molecule in the signaling pathway regulating PMN degranulation. We hypothesized that polymorphisms affect the expression level of Hck, which, in turn, modulates PMN mediator release and tissue damage and influences the development of COPD. Here we systematically investigated genetic tag polymorphisms of the Hck gene, Hck mRNA and protein expression pattern in PMNs, and PMN mediator release (myeloperoxidase) in 60 healthy white subjects, and assessed their association with the use of several genetic models. The association of genetic polymorphisms with COPD-related phenotypes was determined in the lung healthy study cohort (LHS). We identified a novel 15 bp insertion/deletion polymorphism (8,656 L/S) in intron 1 of the Hck gene, which was associated with differential expression of Hck protein and PMN myeloperoxidase release. In the LHS cohort, there was significant interaction between the 8,656 L/S polymorphism and smoking on baseline lung function and 8,656 L/S was associated with bronchodilator response. These data suggest that the insertion/deletion polymorphism could be a functional polymorphism of the Hck gene, may contribute to COPD pathogenesis and modify COPD-related phenotypes.

Changing the burden of COPD mortality

COPD is a major cause of mortality and morbidity worldwide with an estimated 2.75 million deaths in 2000 (fourth leading cause of death). In addition to the considerable morbidity and mortality associated with COPD, this disease incurs significant healthcare and societal costs. Current COPD guidelines acknowledge that the following can improve COPD mortality: smoking cessation; long-term oxygen therapy; and lung volume reduction surgery in small subsets of COPD patients. To date, no randomized controlled trials have demonstrated an effect of pharmacological treatment on mortality, although several observational studies suggest that both long-acting bronchodilators and inhaled corticosteroids may provide a survival benefit. The possibility that these treatments reduce mortality is being investigated in ongoing large-scale clinical trials.

Effect of treatments on the progression of COPD: report of a workshop held in Leuven, 11-12 March 2004

During the last decade several long term studies of interventions in patients with COPD have been published. This review analyses the potential of these interventions to alter the progression of the condition. The only treatment that has unequivocally been shown to reduce the rate of decline in FEV(1) is smoking cessation. Active psychological intervention in combination with pharmacotherapy is required. Other treatments may have an effect on the rate of decline in FEV(1) but this appears to be very small, at most. Several treatments affect the exacerbation rate and therefore might affect the progression of the disease. Further studies are warranted to examine this effect.