Characteristics of COPD in never-smokers and ever-smokers in the general population: results from the CanCOLD study.

BACKGROUND: There is limited data on the risk factors and phenotypical characteristics associated with spirometrically confirmed COPD in never-smokers in the general population. AIMS: To compare the characteristics associated with COPD by gender and by severity of airway obstruction in never-smokers and in ever-smokers. METHOD: We analysed the data from 5176 adults aged 40 years and older who participated in the initial cross-sectional phase of the population-based, prospective, multisite Canadian Cohort of Obstructive Lung Disease study. Never-smokers were defined as those with a lifetime exposure of <1/20 pack year. Logistic regressions were constructed to evaluate associations for 'mild' and 'moderate-severe' COPD defined by FEV1/FVC <5th centile (lower limits of normal). Analyses were performed using SAS V.9.1 (SAS Institute, Cary, North Carolina, USA). RESULTS: The prevalence of COPD (FEV1/FVC

Exacerbation-like respiratory symptoms in individuals without chronic obstructive pulmonary disease: results from a population-based study.

RATIONALE: Exacerbations of COPD are defined clinically by worsening of chronic respiratory symptoms. Chronic respiratory symptoms are common in the general population. There are no data on the frequency of exacerbation-like events in individuals without spirometric evidence of COPD. AIMS: To determine the occurrence of 'exacerbation-like' events in individuals without airflow limitation, their associated risk factors, healthcare utilisation and social impacts. METHOD: We analysed the cross-sectional data from 5176 people aged 40 years and older who participated in a multisite, population-based study on lung health. The study cohort was stratified into spirometrically defined COPD (post-bronchodilator FEV1/FVC < 0.7) and non-COPD (post bronchodilator FEV1/FVC ≥ 0.7 and without self-reported doctor diagnosis of airway diseases) subgroups and then into those with and without respiratory 'exacerbation-like' events in the past year. RESULTS: Individuals without COPD had half the frequency of 'exacerbation-like' events compared with those with COPD. In the non-COPD group, the independent associations with 'exacerbations' included female gender, presence of wheezing, the use of respiratory medications and self-perceived poor health. In the non-COPD group, those with exacerbations were more likely than those without exacerbations to have poorer health-related quality of life (12-item Short-Form Health Survey), miss social activities (58.5% vs 18.8%), miss work for income (41.5% vs 17.3%) and miss housework (55.6% vs 16.5%), p<0.01 to <0.0001. CONCLUSIONS: Events similar to exacerbations of COPD can occur in individuals without COPD or asthma and are associated with significant health and socioeconomic outcomes. They increase the respiratory burden in the community and may contribute to the false-positive diagnosis of asthma or COPD.

Persistency of Pseudomonas aeruginosa in sputum cultures and clinical outcomes in adult patients with cystic fibrosis.

Our objective was to describe the natural history of infection with transmissible and unique strains of P. aeruginosa (PA) in adult CF patients and to determine if clearance of PA from sputum was associated with an improvement in clinical status. This was a 3-year prospective cohort study of adult patients with CF. Sputum was collected at baseline and annually. Rate of decline of FEV1, BMI, exacerbation rate, and time to death or transplant were compared between patients who cleared PA versus those in whom PA was persistent. A total of 373 patients were included in the study, 75% were infected with PA at baseline; 24% were infected with transmissible strains and 51% with unique strains. Patients infected with unique strains were more likely to clear PA from their sputum over 3 years compared to those infected with transmissible strains (19% vs 10%, P=0.05). Declines in FEV1 and rates of pulmonary exacerbations, deaths, or lung transplants were not different between patients who cleared PA compared to those who remained persistently infected. No clinical benefit was identified in patients who cleared PA from sputum compared to those who remained persistently infected.

Comparison of three typing methods for Pseudomonas aeruginosa isolates from patients with cystic fibrosis.

The aim of this study was to compare two traditional pattern matching techniques, pulsed-field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD), with the more reproducible technique of multilocus sequence typing (MLST) to genotype a blinded sample of Pseudomonas aeruginosa isolates from cystic fibrosis (CF) patients. A blinded sample of 48 well-characterized CF P. aeruginosa isolates was genotyped by PFGE, RAPD, and MLST, each performed in a different laboratory. The discriminatory power and congruence between the methods were compared using the Simpson's index, Rand index, and Wallace coefficient. PFGE and MLST had the greatest congruence with the highest Rand index (0.697). The discriminatory power of PFGE, RAPD, and MLST were comparable, with high Simpson's indices (range 0.973-0.980). MLST identified the most clonal relationships. When clonality was defined as agreement between two or more methods, MLST had the greatest predictive value (100 %) in labeling strains as unique, while PFGE had the greatest predictive value (96 %) in labeling strains as clonal. This study demonstrated the highest level of agreement between PFGE and MLST in genotyping P. aeruginosa isolates from CF patients. MLST had the greatest predictive value in identifying strains as unique and, thus, has the potential to be a cost-efficient, high-throughput, first-pass typing method.

Recurrent first hitting times in Wiener diffusion under several observation schemes.

Recurrent events are commonly encountered in the natural sciences, engineering, and medicine. The theory of renewal and regenerative processes provides an elegant mathematical foundation for idealized recurrent event processes. In real-world applications, however, the contexts tend to be complicated by a variety of practical intricacies, including observation schemes with different phase and data structures. This paper formulates a recurrent event process as a succession of independent and identically distributed first hitting times for a Wiener sample path as it passes through successive equally-spaced levels. We develop exact mathematical results for statistical inferences based on several observation schemes that include observation initiated at a renewal point, observation of a stationary process over a finite window, and other variants. We also consider inferences drawn from different data structures, including gap times between renewal points (or fragments thereof) and counts of renewal events occurring within an observation window. We explore the precision of estimates using simulated scenarios and develop empirical regression functions for planning the sample size of a recurrent event study. We demonstrate our results using data from a clinical trial for chronic obstructive pulmonary disease in which the recurrent events are successive exacerbations of the condition. The case study demonstrates how covariates can be incorporated into the analysis using threshold regression.

Confirmation of asthma in an era of overdiagnosis.

It was recently shown that 30% of adults with a physician diagnosis of asthma did not have asthma when objectively assessed using a four-step algorithm involving serial spirometry, bronchial challenge testing and subsequent tapering of asthma medications. The objective of the present study was to determine how many steps in the algorithm were required in order to confirm asthma, and whether any patient-related variables were associated with earlier asthma confirmation. A total of 540 subjects with a previous physician diagnosis of asthma were randomly recruited from the community. The number of subjects confirmed with asthma at each study visit was calculated. Regression analysis was used to determine variables associated with earlier asthma confirmation. Of the 499 subjects who completed the diagnostic algorithm, 346 (69%) had asthma confirmed and 150 (30%) had asthma excluded. Of subjects in whom asthma was confirmed, including those using regular asthma controlling medications, >90% were confirmed with only one or two study visits, by either pre- and post-bronchodilator spirometry or a single bronchial challenge test. Only 46 (9%) out of 499 subjects required tapering of asthma medications and repeated bronchial challenge tests for exclusion or confirmation of asthma. Lower forced expiratory volume in 1 s and younger age were associated with earlier asthma confirmation. For the majority with a previous physician diagnosis of asthma, only pre- and post-bronchodilator spirometry and a single methacholine challenge test are required in order to confirm asthma.

The implementation of rifapentine and isoniazid (3HP) in two remote Arctic communities with a predominantly Inuit population, the Taima TB 3HP study.

Background: The incidence of TB among Inuit is the highest in Canada. A significantly shorter latent TB infection (LTBI) treatment with rifapentine and isoniazid once weekly for 12 weeks (3HP) is now available in limited settings in Canada.Methods: A prospective open-label 2-year observational postmarketing study was conducted introducing 3HP for the first time in Canada in Iqaluit followed by a program rollout in Qikiqtarjuaq, Nunavut.Results: A total of 247 people were offered 3HP, 102 in the Iqaluit postmarketing study and 145 in the Qikiqtarjuaq program roll out. Although statistical significance was not reached, more people who started treatment completed treatment in the 3HP group (Iqaluit, 60/73 (82.2%) and Qikiqtarjuaq, 89/115 (77.4%)) than in the historical control 9INHgroup (306/420 = 72.9%) (p = 0.2). Most of the adverse events in 3HP treated patients were associated with mild discomfort but no disruption of normal daily activity. Not drinking alcohol was associated with increased 3HP completion (OR 13.33, 95% CI, 2.27-78.20) as was not taking concomitant medications (OR 7.19, 95% CI, 1.47-35.30).Conclusions: The present study supports the feasibility and safety profile of 3HP for the treatment of LTBI in Nunavut.

Combination antibiotic susceptibility of biofilm-grown Burkholderia cepacia and Pseudomonas aeruginosa isolated from patients with pulmonary exacerbations of cystic fibrosis.

We identified double and triple antibiotic combinations effective against biofilm-grown Burkholderia cepacia and Pseudomonas aeruginosa sampled from cystic fibrosis (CF) patients undergoing acute pulmonary exacerbations. Sputum bacteria from 110 CF patients were grown as biofilms. Combination antibiotic susceptibility testing was used to test 94 double and triple antibiotic combinations. Biofilm-grown bacterial isolates were less susceptible to antibiotic combinations compared to the same bacterial isolates grown planktonically (P < 0.001). Fifty-nine percent of biofilm-grown B. cepacia isolates and 29% of P. aeruginosa isolates were resistant to all double antibiotic combinations tested. Triple antibiotic combinations were more effective than double antibiotic combinations against biofilms (P < 0.0001). For P. aeruginosa biofilms, the addition of azithromycin or rifampin to otherwise effective antibiotic combinations was frequently associated with antagonism. Bacterial biofilms of CF organisms are highly resistant to antibiotics. This study identified potentially effective antibiotic combinations to guide the empirical treatment of CF pulmonary exacerbations.

Feasibility of a structured 3-minute walk test as a clinical decision tool for patients presenting to the emergency department with acute dyspnoea.

INTRODUCTION: Emergency department (ED) physicians face frequent decisions on whether to admit patients with congestive heart failure (CHF) or acute exacerbation of chronic obstructive pulmonary disease (COPD). This feasibility study evaluated the potential of a structured 3-minute walk test as a clinical decision tool for admission and correlated its performance with poor clinical outcomes. It also aimed to gather evidence and directions for the design of a multicentre study to derive clinical guidelines. METHODS: In this prospective cohort study, a convenience sample was enrolled of 40 adult patients who presented to a tertiary care ED with CHF, COPD, or stable chest pain and were being considered for discharge. Patients walked at their own pace and their dyspnoea, respiratory rate, heart rate and oxygen saturation were recorded each minute for 4 minutes. The primary outcome was "poor clinical outcome" defined as admission to hospital, the need for biphasic positive airway pressure, the need for intubation, relapse, or death. RESULTS: 85.0% successfully completed the test and 30.0% had poor clinical outcomes. Of those with poor clinical outcomes, 41.7% were unable to complete the test compared with only 3.6% of those with good clinical outcomes (p<0.01). Significant differences were noted in the dyspnoea (p = 0.04) and respiratory rate (p = 0.03) as well as oxygen saturation measurements at 3 minutes. CONCLUSIONS: The 3-minute walk test is a non-resource intensive, simple procedure with applicability in most ED for discharge decisions in patients with cardiopulmonary conditions. Multicentre studies are being planned to validate these findings and establish guidelines for admission and discharge of patients with CHF or acute exacerbation of COPD.

Cost effectiveness of therapy with combinations of long acting bronchodilators and inhaled steroids for treatment of COPD.

BACKGROUND: Little is known about the combination of different medications in chronic obstructive pulmonary disease (COPD). This study determined the cost effectiveness of adding salmeterol (S) or fluticasone/salmeterol (FS) to tiotropium (T) for COPD. METHODS: This concurrent, prospective, economic analysis was based on costs and health outcomes from a 52 week randomised study comparing: (1) T 18 microg once daily + placebo twice daily (TP group); (2) T 18 microg once daily + S 25 microg/puff, 2 puffs twice daily (TS group); and (3) T 18 microg once daily + FS 250/25 microg/puff, 2 puffs twice daily (TFS group). The incremental cost effectiveness ratios (ICERs) were defined as incremental cost per exacerbation avoided, and per additional quality adjusted life year (QALY) between treatments. A combination of imputation and bootstrapping was used to quantify uncertainty, and extensive sensitivity analyses were performed. RESULTS: The average patient in the TP group generated CAN$2678 in direct medical costs compared with $2801 (TS group) and $4042 (TFS group). The TS strategy was dominated by TP and TFS. Compared with TP, the TFS strategy resulted in ICERs of $6510 per exacerbation avoided, and $243,180 per QALY gained. In those with severe COPD, TS resulted in equal exacerbation rates and slightly lower costs compared with TP. CONCLUSIONS: TFS had significantly better quality of life and fewer hospitalisations than patients treated with TP but these improvements in health outcomes were associated with increased costs. Neither TFS nor TS are economically attractive alternatives compared with monotherapy with T.

Counting, analysing and reporting exacerbations of COPD in randomised controlled trials.

BACKGROUND: Clinical trials measure exacerbations of chronic obstructive pulmonary disease (COPD) inconsistently. A study was undertaken to determine if different methods for ascertaining and analysing COPD exacerbations lead to biased estimates of treatment effects. METHODS: Information on the methods used to count, analyse and report COPD exacerbation rates was abstracted from clinical trials of long-acting bronchodilators or long-acting bronchodilator/inhaled steroid combination products published between 2000 and 2006. Data from the Canadian Optimal Therapy of COPD Trial was used to illustrate how different analytical approaches can affect the estimate of exacerbation rates and their confidence intervals. RESULTS: 22 trials (17,156 patients) met the inclusion criteria and were reviewed. None of the trials adjudicated exacerbations or determined independence of events. 14/22 studies (64%) introduced selection bias by not analysing outcome data for subjects who prematurely stopped study medications. Only 31% of trials used time-weighted analyses to calculate the mean number of exacerbations/patient-year and only 15% accounted for between-subject variation. In the Canadian Optimal Therapy of COPD Trial the rate ratio for exacerbations/patient-year was 0.85 when all data were included in a time-weighted analysis, but was overestimated as 0.79 when data for those who prematurely stopped study medications were excluded and was further overestimated as 0.46 when a time-weighted analysis was not conducted; p values ranged from 0.03 to 0.24 depending on how exacerbations were determined and analysed. CONCLUSIONS: Clinical trials have used widely different methods to define and analyse COPD exacerbations and this can lead to biased estimates of treatment effects. Future trials should strive to include blinded adjudication and assessment of the independence of exacerbation events, and trials should report time-weighted intention-to-treat analyses with adjustments for between-subject variation in COPD exacerbations.

Methodological issues in therapeutic trials of COPD.

The recent Towards a Revolution in COPD Health (TORCH) randomised trial replicated the findings of previous trials in chronic obstructive pulmonary disease (COPD) on the apparent effectiveness of inhaled corticosteroids (ICS) in reducing exacerbation rates, but not so for mortality. In the present article, the authors review methodological issues in the TORCH and previous trials, such as patients already receiving ICS before randomisation and the absence of follow-up after study drug discontinuation, using data from two trials. First, among previous ICS users in the Canadian Optimal Therapy of COPD Trial, the hazard ratio of the first exacerbation with ICS relative to bronchodilators was 0.71 (95% confidence interval (CI) 0.53-0.96), while among those not using ICS prior to randomisation, it was 1.11 (95% CI 0.69-1.79). Secondly, the rate ratio of exacerbations with ICS was 0.78 (95% CI 0.61-0.99) prior to drug discontinuation during follow-up and 1.23 (95% CI 0.78-1.95) thereafter. Finally, a 2x2 factorial analysis of the TORCH data found a rate ratio of mortality for the salmeterol component to be 0.83 (95% CI 0.74-0.95), while for the fluticasone component it was 1.00 (95% CI 0.89-1.13). In conclusion, after proper consideration of the various methodological shortcomings in the design and analysis of randomised trials, the effectiveness of inhaled corticosteroids in treating chronic obstructive pulmonary disease remains doubtful, while the benefit observed with combination therapy may be due exclusively to the beneficial effects of the long-acting bronchodilator alone.

Evaluating the risk of pneumonia with inhaled corticosteroids in COPD: Retrospective database studies have their limitations SA.

An increased risk of non-fatal pneumonia has been documented in COPD patients treated with inhaled corticosteroids (ICS) in randomized clinical trials. Retrospective database analyses have been conducted to evaluate this signal in larger populations treated in the community. To understand how methodological choices may influence results in observational studies, we compared two recent Canadian studies which used health administrative databases from Quebec and Ontario and came to opposite conclusions on the risk of pneumonia in ICS treated COPD patients. Explanations for why the results of these studies diverged are explored. The Suissa analysis used RAMQ data from Quebec and showed an increased relative risk of serious pneumonia for current users of ICS compared to non users, RR = 1.69 (95% confidence interval, 1.63-1.75). The Gershon analysis used ODB data and showed no difference for pneumonia hospitalisation, RR = 1.01 (0.93-1.08). Reasons for differences in study findings include lack of validated definitions of COPD, poor selection of relevant exposure groups, channeling and confounding biases, and failure to perform on-treatment analyses for safety. CONCLUSION: Our study identifies methodological features that need consideration to increase robustness and minimize threats to internal validity of retrospective health administrative database studies.

Lost in translation? How adults living with Cystic Fibrosis understand treatment recommendations from their healthcare providers, and the impact on adherence to therapy.

OBJECTIVE: This study builds on the limited research documenting Cystic Fibrosis (CF) patients' understanding of treatment recommendations and how this may impact adherence to therapy. METHODS: We surveyed adults with CF and their healthcare professional (HCP) to capture treatment recommendations provided by the HCP, and patients' knowledge, and frequency of performance, of these recommendations. We classified CF participants' understanding of treatment recommendations (correct/incorrect) as compared to the actual recommendations made by the HCP. We computed CF participants' adherence in relation to HCP treatment recommendations and to their own understanding of treatment recommendations (adherent/non-adherent). RESULTS: Complete HCP and patient data were available for 42 participants. The recommended treatment frequency was correctly understood by 0%-87.8% of CF participants. Adherence to HCP treatment recommendations ranged from 0 to 68.3% (mean 45.4%±21.5), and rates were low (<33%) for acapella, percussion/postural drainage, tobramycin nebulization and insulin. Participants' adherence was greater when calculated in relation to participants' understanding of treatment recommendations (62.4%±25.1) than when calculated in relation to actual HCP treatment recommendations (45.4%±21.5%) (p=0.009). CONCLUSION AND PRACTICE IMPLICATIONS: Adults with CF misunderstand treatment recommendations; this likely affects treatment adherence. Interventions to ensure HCPs use effective communication strategies are needed.

Low molecular weight heparin decreases proximal and distal deep venous thrombosis following total knee arthroplasty. A meta-analysis of randomized trials.

OBJECTIVES: To assess the efficacy and safety of low molecular weight heparin (LMWH) as deep venous thrombosis (DVT) prophylaxis following total knee arthroplasty. DATA SOURCES: Medline 1986 to June 1997, Embase, and manufacturers were used to identify randomized controlled trials. REVIEW METHODS: Trials included were randomized studies of LMWH with routine radiological screening for DVT. Placebo or active controls were included. Two reviewers independently screened trials for inclusion, and assessed their quality. Pooled relative risk estimates of DVT and proximal DVT rates were calculated using a DerSimonian and Laird random effects model. Sensitivity of the results to the type of control used and the quality of the trial was assessed. RESULTS: The relative risk of DVT for a patient given LMWH is 0.73 (95% CI 0.66 to 0.80) when compared with patients treated with adjusted dose heparin or warfarin controls. The relative risk for proximal DVT is 0.58 (95% CI 0.38 to 0.90). The relative risk of pulmonary emboli in the LMWH group was 0.55 (95% C.I. 0.20 to 1.57). No excess of bleeding was recorded in the LMWH group. CONCLUSIONS: Low molecular weight heparin is more efficacious than either adjusted dose heparin or adjusted dose warfarin, when used to prevent DVT and proximal DVT following total knee arthroplasty.

Bronchogenic carcinoma in patients seropositive for human immunodeficiency virus.

The purpose of this report is to describe an association between bronchogenic carcinoma and HIV. Three HIV-seropositive patients are described who developed bronchogenic cancer (two large cell, one adenocarcinoma) before developing an AIDS-defining illness. A critical review of the literature revealed 22 other patients in which the association of HIV infection and lung cancer is reported. These patients are characterized by a relatively young age at diagnosis (median, 43 years) and prevalence of the adenocarcinoma subtype (13 of 25 patients). Twenty of 21 patients had a history of smoking. Among 21 patients for whom data were available, 6 patients (28 percent) had AIDS at time of diagnosis of lung cancer while 11 patients (55 percent) did not have AIDS or AIDS-related complex at diagnosis.

How accurate is spirometry at predicting restrictive pulmonary impairment?

OBJECTIVE: To determine the accuracy with which spirometric measurements of FVC and expiratory flow rates can diagnose the presence of a restrictive impairment. DESIGN: The pulmonary function tests of 1,831 consecutive white adult patients who had undergone both spirometry and lung volume measurements on the same visit over a 2-year period were analyzed. The probability of restrictive pulmonary impairment, defined as a reduced total lung capacity (TLC) below the lower limit of the 95% confidence interval, was determined for each of several categoric classifications of the spirometric data, and additionally for each of several interval levels of the FVC and the FEV1/FVC ratio. SETTING: A large clinical laboratory in a university teaching hospital using quality-assured and standardized spirometry and lung volume measurement techniques according to American Thoracic Society standards. RESULTS: Two hundred twenty-five of 1,831 patients (12.3%) had a restrictive defect. The positive predictive value of spirometry for predicting restriction was relatively low; of 470 patients with a low FVC on spirometry, only 41% had restriction confirmed on lung volume measurements. When the analysis was confined to the 264 patients with a restrictive pattern on spirometry (ie, low FVC and normal or above normal FEV1/FVC ratio), the positive predictive value was 58%. Conversely, spirometry had a very favorable negative predictive value; only 2.4% of patients (32 of 1,361) with a normal vital capacity (VC) on spirometry had a restrictive defect by TLC measurement. The probability of a restrictive defect was directly and linearly related to the degree of reduction of FVC when the FVC was < 80% of predicted (p = 6.002). Combining the FVC and the FEV1/FVC ratio improved the predictive ability of spirometry; for all values of FVC < 80% of the predicted amount, the likelihood of restrictive disease increased as the FEV1/FVC ratio increased. CONCLUSIONS: Spirometry is very useful at excluding a restrictive defect. When the VC is within the normal range, the probability of a restrictive defect is < 3%, and unless restrictive lung disease is suspected a priori, measurement of lung volumes can be avoided. However, spirometry is not able to accurately predict lung restriction; < 60% of patients with a classical spirometric restrictive pattern had pulmonary restriction confirmed on lung volume measurements. For these patients, measurement of the TLC is needed to confirm a true restrictive defect.

Persistent hypoxemia occurring as a complication of tricuspid valve endocarditis.

A 33-year-old woman had intravenous drug-associated tricuspid valve infective endocarditis. Despite resolution of septic pulmonary emboli, hypoxemia persisted. We report a case of right-to-left shunting across a previously insignificant patent foramen ovale documented by contrast transesophageal echocardiography. Although a rare complication of tricuspid endocarditis, clinicians should be aware of this potential correctable complication.

Management of steroid-dependent asthma with methotrexate: a meta-analysis of randomized clinical trials.

Our objective was to determine whether methotrexate is an effective steroid-sparing agent for patients with severe asthma. Published reports of controlled trials assessing the use of methotrexate in asthma were identified by a search of the MEDLINE, EMBASE, CINAHL, Biological Abstracts on CD, and Current Contents databases. Bibliographies from identified studies and from review articles were manually searched. Published and unpublished reports in any language were identified and assessed for inclusion in the meta-analysis. We selected randomized, double-blind, placebo-controlled trials in which low-dose methotrexate was administered to corticosteroid-dependent asthmatics, and oral steroids were subsequently tapered according to the patients' clinical status. Data were extracted independently by two reviewers. For all eligible trials, the mean reduction in oral corticosteroid dose, the mean change in FEV1, and the standard deviations, were calculated for the treatment and control groups. Data concerning side-effects of therapy were also extracted. Data from 12 studies, reporting on a total of 250 patients, were pooled using a weighted average method, with weights proportional to the inverse of the variance of the treatment effect. Compared to placebo, the use of methotrexate was associated with a pooled 6.0% improvement in FEV1 (95% CI, 1.0-11%) and an 18.2% reduction in oral steroid use (95% CI, 11.7-24.7%). This corresponded to a 3.3 mg day-1 greater reduction in oral steroid use for patients taking methotrexate than for those taking placebo (95% CI, 2.1-4.4 mg day-1). Gastrointestinal complications and transient increases in liver enzymes were more common in patients randomized to methotrexate. Three potentially life-threatening side-effects (two pneumonias and one liver dysfunction) occurred in 159 patients randomized to methotrexate vs. none in those patients on placebo. It was concluded that methotrexate allowed a modest reduction in oral corticosteroid compared to patients receiving placebo. The benefit is relatively small, however, and should be balanced against the potential for side-effects associated with the use of methotrexate.

A threshold regression model for recurrent exacerbations in chronic obstructive pulmonary disease.

OBJECTIVE: Respiratory exacerbations are a major source of morbidity in patients with chronic obstructive pulmonary disease (COPD). In this article, we model COPD health status as a formal stochastic process. A successful model will provide a suitable statistical structure for analysis of the effects of medical interventions on a patient's health status, and, possibly, offer new insights into the underlying disease process. STUDY DESIGN AND SETTING: Our approach uses a regression methodology for time-to-event data called threshold regression (TR). We test the methodology on COPD data from a randomized clinical trial. Two TR models are studied: one based on a Poisson process and the other, a Wiener diffusion process. RESULTS: Both models provide reasonably accurate fits to the clinical trial data. The insights offered by the fitted models are interpreted. Analysis of the clinical trial data set using these TR models revealed that patients who experienced multiple exacerbations showed a progressive acceleration in rate of exacerbations, and successive shortening of stable intervals between exacerbations. CONCLUSION: TR techniques allow for realistic modeling of the COPD health state. A hybrid Poisson/Wiener diffusion TR model that incorporates the causal determinants of disease operating in each patient may be preferable.