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Wilt TJ, Niewoehner D, Kim CB, et al. Use of Spirometry for Case Finding, Diagnosis, and Management of Chronic Obstructive Pulmonary Disease (COPD). Rockville (MD): Agency for Healthcare Research and Quality (US); 2005 Sep. (Evidence Reports/Technology Assessments, No. 121.)

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

Cover of Use of Spirometry for Case Finding, Diagnosis, and Management of Chronic Obstructive Pulmonary Disease (COPD)

Use of Spirometry for Case Finding, Diagnosis, and Management of Chronic Obstructive Pulmonary Disease (COPD).

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Topic Assessment and Refinement and Literature Review

We began the review process conferencing with the AHRQ and the nominee partners (ATS, AAFP, ACP, and the AAP) to clarify the scope of the project and other background information. Seven clinical experts also agreed to serve as members of a technical expert panel group (TEP, See Appendix A *). The comments and suggestions provided by the TEP clarified the conceptual framework and refined study questions used for the project. Based on our initial conference calls we developed a comprehensive work plan that covered an assessment and refinement of study questions and proposed literature search and review, inclusion/exclusion criteria, methods for evaluating the quality of studies, and rating the strength of evidence.

Analytic Framework

An analytic framework was developed that assesses the key questions along the causal pathway of case finding, diagnosis, treatment, and outcomes (Figure 1 on page 14). The framework describes the logical chain that should be supported by evidence to link spirometry to improved health outcomes. It takes the perspective of adults presenting to primary health care settings based on smoking and symptom status. It evaluates pathways related to the spirometric and symptom status and potential benefits or harms of therapeutic interventions.

Figure 1. Spirometry for case finding of COPD—analytic framework.


Figure 1. Spirometry for case finding of COPD—analytic framework.

Question 1 What is the prevalence of chronic obstructive pulmonary disease (COPD) and airflow obstructions in various adult populations as defined by: 1) spirometry and 2) clinical examination?

Diagnosis and case-finding recommendations for spirometric testing include all adults with a history of exposure to risk factors including current and former smokers and any adult with persistent respiratory symptoms of cough, phlegm, wheeze, or dyspnea. Because smoking is the main risk factor in causing COPD, the analytic framework begins with adults presenting to a primary care clinic where an assessment of COPD risk factors (smoking and symptom status) is performed. Decision nodes are based on smoking and respiratory status. Spirometry characterizes an individual as having airflow obstruction (and the stage of severity) while history and physical examination assess the presence or absence of signs or symptoms. Among former and current smokers, spirometry would be utilized regardless of symptom status (case-finding in asymptomatic individuals or those with nonspecific symptoms). Thus, the prevalence of abnormal spirometry in these two groups regardless of symptom status is assessed and subsequently the prevalence of individuals within each spirometric category that have respiratory symptoms. In adults that have never smoked, proposed spirometric recommendations are limited to those with respiratory symptoms. An unknown percentage of individuals might not be diagnosed or would be misdiagnosed in the absence of spirometry. Spirometry may detect a large reservoir of asymptomatic individuals, those with mild airflow limitation, or individuals with minimal symptoms that might not benefit from detection and treatment. Adverse effects would include increased health care costs, distraction from other interventions of proven effectiveness, or labeling individuals with disease unnecessarily or incorrectly. Spirometry could create unnecessary patient worry, increase health care expense and use of ineffective therapies with adverse effects, provide false reassurance, or lead to lower utilization of treatments of known effectiveness for other conditions.12

The analytic framework takes the perspective that abnormal airflow (as detected by spirometry) is a likely surrogate or risk factor for COPD but is not the sole criterion for defining clinically important disease or adults requiring treatment. Compared to clinical evaluation, spirometry would be useful if it improved diagnostic accuracy of individuals with airflow obstruction who would benefit from disease-specific interventions and ruled out individuals who are otherwise being misdiagnosed and/or receiving ineffective/unnecessary treatment. Improvement in process measures include increased smoking cessation rates and more appropriate utilization of effective interventions. Clinical outcomes include improved respiratory symptoms, health status, morbidity, and mortality in the spirometrically tested group. Determining the prevalence and severity of airflow obstruction in primary care adults according to symptom and smoking status and prior clinical diagnosis is necessary to assess the number of individuals that may benefit (or be harmed) by spirometric case-finding and diagnosis compared to clinical examination.

Definitions of “airflow obstruction” and “lower limits of normal” vary and typically have become more expansive over time. Normal lung function (and thus criteria for airflow obstruction) has been statistically derived from population-based surveys rather than directly based on pathological/clinical criteria of disease.13 Spirometrically-detected airflow impairment has been defined using equations according to subjects having an FEV1/FVC ratio below the lowest 5 percent of the reference population (controlled for gender, height, age, and race) rather than documenting a disease state or symptom status. Most population based surveys have not conducted bronchodilator reversibility testing and thus estimates of a patient's best lung function or the presence of asthma or partial reversibility in airflow obstruction may not be accurately known. Additionally, airflow obstruction as measured by spirometry does not fully describe the disability in COPD that is manifested by dyspnea, exercise intolerance, and exacerbations. Some individuals with airflow obstruction are asymptomatic. Others with respiratory symptoms compatible with COPD may have normal spirometry. This may be due to the fact that other physiologic abnormalities (dynamic hyperinflation of the lungs and peripheral muscle abnormalities) as well as psychologic variables (coexisting anxiety) affect these clinical outcomes. Even among symptomatic individuals with airflow obstruction other conditions may be the cause of the respiratory symptoms (e.g., heart failure).

GOLD has developed recommendations for the diagnosis, management, and prevention of COPD. Their recommendations rely on results of spirometry in addition to clinical evaluation (e.g., physical examination, chest x-ray, eliciting symptoms based on clinical history).8 Diagnosis and treatment include individuals without respiratory symptoms but who have airflow obstruction. Changing definitions of disease can profoundly alter disease prevalence.14 In the case of COPD, this could occur by classifying individuals with disease based solely on spirometric findings rather than a combination of symptoms and physiologic measures or changing the level of spirometry that constitutes the presence or severity of disease. Table 1 on page 7 reflects the effects of using varying spirometric definitions of airflow obstruction. The effect of new definitions on disease prevalence/incidence, symptom severity, treatment, and outcomes is not known.

Table 1. A comparison of four sets of staging criteria for COPD*.

Table 1

A comparison of four sets of staging criteria for COPD*.

Clinically significant COPD includes individuals with dyspnea or other respiratory symptoms that reduce quality of life. Spirometry may be useful to assess the presence and severity of airflow obstruction, determine if symptoms are likely due to COPD (both in confirming a diagnosis and establishing spirometric severity or in excluding airflow obstruction as a cause), and institute appropriate disease-specific intervention. In the absence of airflow obstruction, a clinical diagnosis of and treatment for COPD is inappropriate (though individuals with asthma or a large bronchodilator response may have normal spirometry during symptom free periods). Assessing airflow in the absence of disabling symptoms or effective preventive interventions is limited to prognostic information or improving smoking cessation rates.

Question 2 Can use of spirometry lead to increased smoking cessation rates?

Smoking cessation is the most effective way to reduce the risk of developing COPD and prevent or improve respiratory symptoms. While smokers with symptoms have the greatest improvement, reduction in future respiratory symptoms is seen even among asymptomatic individuals with airflow obstruction.15 It is the only intervention demonstrated to prevent or delay the development of airflow limitation and reduce its progression. In patients with mild to moderate airflow obstruction, abstinence from smoking results in a sustained 50 percent reduction in the rate of lung-function decline over time.16

Clinical Practice Guidelines issued by the U.S. Department of Health and Human Services17 recommend that health care providers identify all smokers and advise them to quit regardless of spirometric or symptom status. Individuals attempting to quit smoking should be offered pharmacological interventions, unless there are medical reasons to withhold this form of treatment. Interventions that improve smoking cessation rates and maintain abstinence would be very valuable. However, reducing the prevalence of smoking has proven to be a formidable task.18 Approximately 35 percent of smokers with mild to moderate airflow obstruction enrolled in the Lung Health Study achieved abstinence at 1 year, but only 22 percent reported continued abstinence at 5 years. The 16 percent absolute reduction compared to enrollees assigned to receive “usual care” occurred with an intensive intervention that consisted of nicotine replacement (chewing gum, inhaler, spray, and a transcutaneous patch that was provided free of charge), cessation behavioral counseling, which consisted of 12 group sessions in the first 10 weeks, and a maintenance program for people who quit smoking.19 Cost effectiveness analyses have shown that smoking cessation interventions with incremental quit rates of 3 percent to 6 percent are economically acceptable because of the large health benefits (many beyond airflow obstruction) due to smoking cessation.4

A key question in case-finding is to determine if obtaining spirometry and providing individuals with measures of their lung function improves smoking cessation rates among current smokers and maintains abstinence among former smokers or never smokers. Benefits could occur regardless of symptom status or spirometric value. The potential roles of spirometry in improving smoking cessation rates include its use as a: 1) “biomarker assessment of lung health” to provide feedback and encouragement for smoking cessation and continued abstinence (regardless of symptom status); 2) risk stratification or prognostic tool for identification of an individual's (or group's) likelihood of smoking cessation, and 3) guide for targeting types of smoking cessation programs. Smoking cessation counseling could be enhanced by incorporating results from spirometric testing into routine clinic visits. Health care providers may be more likely to counsel patients or recommend additional smoking cessation therapies based on spirometric findings. Smokers may be more likely to quit if presented with information about their “lung health.” Adverse effects include added costs and resource use associated with initial and confirmatory spirometric testing and decreased smoking cessation rates due to false reassurance or nihilism. The potential role for, and outcome from, spirometry used as a motivational tool for smoking cessation are shown in Figure 2 on page 15.

Figure 2. Potential role for, and outcomes from, spirometry used as a motivational tool for smoking cessation.


Figure 2. Potential role for, and outcomes from, spirometry used as a motivational tool for smoking cessation.

Question 3 Does the effectiveness of specific therapies to improve clinically relevant outcomes in COPD vary based on baseline or followup spirometry, short-term spirometric response due to initial therapy, or spirometric progression over time?

Treatment goals are to reduce spirometric decline in lung function, relieve disabling respiratory symptoms (particularly dyspnea), improve exercise tolerance and health status, prevent and treat complications and exacerbations, and reduce mortality. Recommendations encourage use of spirometry to assess baseline severity of airflow obstruction and acute treatment response. Clinicians are encouraged to periodically assess symptoms and monitor objective measures of airflow limitation for development of complications and to determine when to adjust therapy. The effectiveness of this strategy is not known.

If treatments are effective in adults with mild to moderate airflow obstruction or those with absent or relatively mild respiratory symptoms, then one potential benefit of case-finding with spirometry could be identification and treatment of a large number of individuals not readily detected by clinical examination. However, if effectiveness is limited to the much smaller cohort of subjects with severe airflow obstruction and activity limiting respiratory symptoms, then population-based spirometric case-finding is less likely to be beneficial compared to spirometric identification and treatment targeted at individuals with bothersome respiratory symptoms.

Spirometry may be useful as a guide for initial and followup management among individuals with established airflow obstruction/COPD. Among asymptomatic individuals, spirometry could be effective if it resulted in initiation of interventions for airflow obstruction that prevented the development of symptoms or reduced the decline in lung function. In symptomatic individuals, spirometry could improve diagnostic accuracy and determination of whether or not spirometric thresholds of airflow obstruction exist prior to appropriate initiation of COPD specific therapy. Monitoring patients with periodic spirometry would be useful if modification of therapeutic interventions according to spirometric response to therapy, spirometric change over time, or achieving a certain spirometric threshold reduced respiratory symptoms including exacerbations and hospitalizations and improved quality of life. Adverse effects would include the costs of using spirometry to monitor treatment or disease progression, harms related to medication use, and unnecessary or improper initiation/modification of treatments based on spirometry compared to clinical evaluation. To assess the effectiveness of interventions for COPD beyond smoking cessation we will focus on whether effectiveness varies according to symptom status (presence or absence, type, severity, or frequency of symptoms), previous clinical diagnosis of COPD, baseline or followup spirometry, acute spirometric response to treatment, spirometric slope over time, and intervention type or dose.

Question 4 Is prediction of prognosis based on spirometry, with or without clinical indicators, more accurate than prognosis based on clinical indicators alone?

Spirometry could provide independent prognosis related to quality of life, progression to more severe and symptomatic COPD, and mortality (both overall and COPD specific). Spirometry may help identify individuals at increased risk for future health problems who are in need of effective COPD-specific interventions. Spirometry may provide more accurate risk stratification and appropriate utilization of interventions for other chronic medical conditions.

The analytic pathway includes the ability of clinical examination and history to determine respiratory symptom status and etiology, spirometry to assess presence and severity of airflow obstruction, spirometry to alter smoking cessation and abstinence rates in current and former smokers, spirometry to guide initiation and modification of pharmacologic or rehabilitation therapy for individuals with established COPD, and finally spirometry as a prognostic tool for future COPD-related outcomes (especially worsening symptom status).

Final synthesis of this information will result in a pathway that evaluates the number of adults needed, according to smoking and symptom status, to receive office-based spirometry in order to identify candidates for treatment. We will estimate the number of individuals likely to have improvement in specific outcomes, the type and relative effectiveness of interventions, whether monitoring of spirometry improves clinical management and outcomes, and prognosis based on spirometric findings.

Literature Search and Data Abstraction

We conducted literature searches for the four key questions simultaneously. Because the individual questions addressed different areas, the search strategies, types of eligible studies, populations, interventions, and outcomes varied for each. The focus of this project was the identification and management of adults with, or at risk for, COPD. Emphasis was placed on studies that assessed outcomes from individuals in primary care or population-based settings of the U.S. according to race, gender, age, smoking, symptom, and spirometric status. Children, individuals with asthma, or alpha-1 antitrypsin disease were excluded.

Question 1

Data sources. Articles published in the English language from 1966 to January 2005 were identified by searching MEDLINE accessed through PubMed and Cochrane Database using the following terms: diagnosis, epidemiology, bronchospirometry, COPD, emphysema, bronchitis, respiratory function tests, airway obstruction (or airflow limitation), cohort studies, case reports, case-control studies. Because our goal was to estimate the prevalence of COPD and airflow obstruction likely to be encountered by casefinding in primary care settings, we examined population based or primary care cohort or case-control studies.

Study selection. Studies were eligible if they reported the results of spirometry testing of community-based adult populations or primary care settings and were published in English. Studies limited to patients with known COPD or symptoms such as cough, sputum production, dyspnea, or wheeze were excluded unless results were reported separately for asymptomatic individuals. Emphasis was placed on community-based studies conducted in the U.S.

Outcomes. The primary outcome was the prevalence of airflow obstruction according to GOLD stage (or other consensus criteria such as ATS) according to: spirometry, race, gender, age, symptom, and smoking status (current, past, or never), and presence of a clinical diagnosis of COPD.

Quality assessment. Quality and strength of evidence was determined by whether the included studies adequately addressed our key outcome by providing information related to spirometrically-detected COPD in general adult populations or primary care settings according to GOLD stage or other consensus criteria, race, gender, age, smoking, and symptom status. Because this report was intended to guide clinical decisions in the United States, we placed greatest emphasis on studies conducted in the U.S.

Question 2

Objective. Our primary goal was to determine if providing smokers with results from spirometric testing improves smoking cessation rates.

Data sources and study selection. A detailed search strategy was used to identify potentially relevant articles and is provided in Appendix B *. Studies were eligible if they were randomized controlled trials (RCTs), published in English, had a minimum of 25 subjects per treatment arm, involved subjects that smoked (regardless of respiratory symptoms or spirometry status), had a followup time of 6 months or longer, and provided outcomes smoking cessation rates (as measured by self-report or biochemical validation such as carbon monoxide level). The intervention had to include spirometry alone or in conjunction with other treatments as a motivational tool for smoking cessation. Studies were excluded if the control group also received notification of spirometric results. Non-controlled reports that merely reported smoking cessation rates according to spirometric value or respiratory status were excluded. However, these studies were reviewed and findings described in order to estimate whether spirometric values or respiratory status could predict smoking cessation rates. Of the 212 references identified, seven met eligibility criteria (Figure 3 on page 16). Additionally, in order to provide a context for potential magnitude and biologic plausibility of various smoking cessation strategies, we included information related to the effectiveness of established strategies for smoking cessation and rationale for use of biomarkers as a tool for enhancing smoking cessation counseling.

Figure 3. Flow chart—Question 2 (smoking cessation)—reference search results.


Figure 3. Flow chart—Question 2 (smoking cessation)—reference search results.

Literature search strategy. The literature search used Ovid MEDLINE until May 2005. To supplement this search, we examined the Cochrane Database of Systematic Reviews of Effectiveness as well as bibliographies of published articles and contacted experts in the field. Listserv members of the World Health Organization's Society for Research on Nicotine and Tobacco were contacted and invited to identify additional published, unpublished, or ongoing relevant studies. Search terms included: spirometry; smoking therapy; smoking psychology; COPD; airflow limitation; randomized controlled trials; controlled clinical trials; and case-control studies. Identified articles were reviewed along with their references to identify other key articles and to refine our search strategy. Our search strategy included articles identified to evaluate the effectiveness of interventions for patients with COPD (Question 3). Titles and abstracts of identified references were reviewed using standardized data abstraction sheets (Appendix C *). All references received an identification number.

Interventions. We considered the process of obtaining and providing the results of spirometry to smokers in combination with focused smoking cessation counseling as a single intervention consistent with a pragmatic approach likely to be employed in health care settings. Other differences in interventions between treatment and control groups such as the incorporation of results from biomarker testing (carbon monoxide or cotinine levels, chest x-rays, etc.), varying frequency, intensity, methods of counseling, or pharmacologic treatments were considered concomitant interventions that might differentially effect cessation rates.

Outcomes. Smoking cessation outcomes in clinical trials are measured in a variety of ways including short- and long-term abstinence and point-prevalent or sustained abstinence. In general, short-term abstinence refers to outcomes at less than 3 months following initiation of treatment and may include in-treatment results, depending on the duration of interventions. Long-term abstinence refers to outcomes measured at 6 to 12 months after initiation of treatment (or later). In addition, at the measurement point, abstinence can be described as point-prevalent (usually 7–30 days prior to the measure) or sustained (ranges from 6 months to continuous from point of intervention). Finally, abstinence can be self-reported, or validated by biomarkers of exposure such as carbon monoxide (CO) or cotinine. Quit attempts are generally regarded as a less robust, secondary process outcome. Our primary outcome was long-term sustained abstinence that was validated by biomarkers. Subgroups of interest included spirometric categories, (e.g., GOLD or ATS), symptom status, race, and gender.

Quality assessment and quantitative synthesis. Quality and strength of evidence was based on the method of Schulz et al.20 We also assessed loss to followup and whether studies provided information that would allow for determination of the independent effect of conducting spirometry and providing their results on smoking cessation rates. Because of the clinical heterogeneity of study interventions, pooled analyses were not conducted.

Question 3

Literature search strategy. Search terms were identical to those published by Sin9 (adults >19 years of age, COPD, RCTs) to identify RCT/controlled clinical trials (CCT), meta-analyses, or reviews published since the completion of their search (i.e., between 2002 and January 2005; for inhaled therapy between 2002 and January 2005). For each of these therapies we conducted a literature search using Ovid MEDLINE. To supplement this search, we examined the Cochrane Database of Systematic Reviews of Effectiveness as well as bibliographies of published articles and contacted experts in the field. We limited our search to English-language articles. These were categorized according to type of intervention: 1) inhaled medications including: β2 agonists, long-acting anticholingerics (tiotropium), combination β agonists and anticholinergics, inhaled corticosteroids, combination inhaled corticosteroids and long-acting β 2 agonists, pulmonary rehabilitation, 2) disease management programs (which include any combination of patient education, enhanced followup, and/or self-management session); 3) long-term administration of non-invasive mechanical ventilation (NIMV); and 4) oxygen therapy.21 We obtained additional information from the data coordinating center for one large trial (LH-1) that evaluated pharmacologic interventions in subjects with mild to moderate airflow obstruction.

Titles and abstracts of identified references in addition to those included in the report by Sin were reviewed using standardized and piloted data abstraction sheets. All references received an identification number. The number of excluded studies and reasons for exclusion are described in Figure 4 on page 16. Studies meeting preliminary eligibility criteria were retrieved in full for further assessment and data extraction.

Figure 4. Flow chart—Treatments for COPD (2002-Jan 2005); inhaled therapies (2002-May 2005)—reference search results.


Figure 4. Flow chart—Treatments for COPD (2002-Jan 2005); inhaled therapies (2002-May 2005)—reference search results.

Eligibility criteria. For intervention studies we restricted our analysis to trials that were randomized, defined by clinical diagnosis or spirometry, and provided clinically relevant outcomes. Trials of inhaled therapies were required to enroll at least 50 subjects per treatment arm. A followup time of 3 months was used as the threshold for inclusion (with the exception of pulmonary rehabilitation programs, for which 6 weeks was used as the threshold).

Studies were excluded if they only reported physiologic variables such as changes in FEV1, because the correlation between spirometric changes and long-term clinical outcomes in COPD has been shown to be weak.22 We examined bibliographies of these reviews and meta-analyses.2337 The studies that contained the different domain of comparison between the baseline and the ending point38 or no baseline data of spirometry as FEV1 39 or no comparison groups at same design,40 or cost-effectiveness analysis41, 42 were excluded. Information from the original publication was used unless additional relevant data were available in subsequent reports.

Quality of studies and strength of evidence. Two researchers independently extracted study and patient characteristics onto data sheets.43 Disagreements were resolved by discussion or cross checking of other co-workers through project meetings.44 The methods of Schulz et al.20 were used to assess the quality of RCT. We evaluated whether studies were blinded, used intention-to-treat analysis, and reported attrition. The magnitude of effect across different outcomes and pharmacologic interventions (e.g., exacerbations, mortality, dyspnea, etc.) was assessed based on absolute and relative reductions as well as in comparison to previously determined minimally important clinical differences in respiratory health status measures. Subgroup analysis was attempted to determine if results varied according to disease severity based on baseline symptom and/or spirometric status, acute change in spirometry, or spirometric change in time. We attempted to focus on individuals most likely to be identified through spirometric casefinding (i.e., individuals with mild to moderate airflow obstruction and respiratory symptoms who were not diagnosed by clinical examination). We evaluated whether any trial utilized spirometry as a guide for monitoring subjects' clinical status or to modify therapy. Of the 53 studies that were eligible, 20 were new references not included in the report by Sin.

Quantitative synthesis of study outcomes. All analyses were conducted using Review Manager Version 4.2 (Revman; The Cochrane Collaboration, Oxford, England). For each end point we combined the results from individual studies to produce pooled effect estimates (relative risk ratios and absolute risk ratios). Heterogeneity of results across individual studies was checked using the Cochrane Q test. If heterogeneity was observed (p<.10), we used the Dersimonian and Laird random-effects model to synthesize the results; otherwise, a fixed-effects model was used.45 As part of a sensitivity analysis for the latter situation, we used a random-effects model to determine the robustness of the data. In all cases, the results obtained from the random-effects and fixed-effects models were similar. Continuous variables were pooled using weighted mean difference technique.

Outcomes. Our primary outcome was the number of individuals with at least one exacerbation as defined by authors. Secondary outcomes included changes in St. George's Respiratory Questionnaire (SGRQ) scale scores; number of subjects with respiratory symptoms including dyspnea, cough, or sputum production; mortality; and overall and respiratory-specific hospitalizations and changes in health status between intervention and control. We attempted to evaluate results according to the following subgroups: spirometrically-determined severity of disease (GOLD or ATS stages and mean baseline FEV1), symptom status, smoking status, gender, age (≥65 vs. <65), and race. We restricted analysis of health status and dyspnea to two well-standardized and validated instruments in COPD, SGRQ Chronic Respiratory Disease Questionnaire (CRQ).46 These instruments quantify the extent of physical and psychological impairments related to COPD and allow investigators to determine the (beneficial) effects of specific interventions on the functional status of patients with COPD.47 Dyspnea and exacerbations are the two most bothersome symptoms and the aspects of COPD that most influence health status. The CRQ is a 20-item COPD specific questionnaire that measures: dyspnea (five items), fatigue (four items), emotion (seven items), and mastery (four items). A 0.5 unit change per question (on a seven-point scale) is considered the minimally important clinical change. Composite scores range from 20–140 with higher scores indicating improved health status. The SGRQ is a respiratory-specific 50 item questionnaire with domains of symptoms, activity, and impacts plus a summary total score. Lower scores indicate improved health status, and a change of four units (out of 100) is considered clinically significant. While validated these questionnaires have been found to have weak correlations with physiologic variables including FEV1 and mild to moderate correlation with exercise capacity and assessment of dyspnea, anxiety, and depression.

Question 4

Data sources and study selection. Articles published in English from 1966-January 2005 were identified using a search strategy similar to Question 1, which also included the key word “prognosis.” Eligible studies included cohort or case-control studies that assessed the prognostic effect of spirometry on COPD progression and outcomes. Additional studies were evaluated to determine the independent effect on overall mortality, though this was not the primary focus as directed by our TEP. We obtained additional results from one of the identified studies through personal communication with the author.

Outcomes. The primary outcome was progression to more severe airflow obstruction (GOLD or other stage criteria) and development of respiratory symptoms.

Data synthesis. Data were described for each study and not pooled.



Note: Appendixes and evidence tables cited in this report are provided electronically at http://www​​.htm


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