Paid employment in subjects with and without chronic obstructive pulmonary disease in five Latin American cities: the PLATINO study.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a costly condition that frequently causes permanent work disabilities. Little information exists regarding the impact of COPD on work force participation and the indirect costs of the disease in developing countries. OBJECTIVE: To examine the frequency of paid employment and factors influencing it in a Latin-American population-based study. METHODS: Post-bronchodilator FEV(1)/FVC < 0.70 (forced expiratory volume in 1 s/forced vital capacity) was used to define COPD. Information regarding paid work was assessed by the question 'At any time in the past year, have you worked for payment?' RESULTS: Interviews were conducted with 5571 subjects; 5314 (759 COPD and 4554 non-COPD) subjects underwent spirometry. Among the COPD subjects, 41.8% reported having paid work vs. 57.1% of non-COPD (P < 0.0001). The number of months with paid work was reduced in COPD patients (10.5 ± 0.17 vs. 10.9 ± 0.06, P < 0.05). The main factors associated with having paid work in COPD patients were male sex (OR 0.33, 95%CI 0.23-0.47), higher education level (OR 1.05, 95%CI 1.01-1.09) and younger age (OR 0.90, 95%CI 0.88-0.92). COPD was not a significant contributor to employment (OR 0.83, 95%CI 0.69-1.00, P = 0.054) in the entire population. CONCLUSIONS: Although the proportion of persons with paid work is lower in COPD, having COPD appears not to have a significant impact on obtaining paid employment in the overall population of developing countries.

Sex-related differences in COPD in five Latin American cities: the PLATINO study.

There is evidence to suggest sex differences exists in chronic obstructive pulmonary disease (COPD) clinical expression. We investigated sex differences in health status perception, dyspnoea and physical activity, and factors that explain these differences using an epidemiological sample of subjects with and without COPD. PLATINO is a cross-sectional, population-based study. We defined COPD as post-bronchodilator forced expiratory volume in 1 s/forced vital capacity ratio <0.70, and evaluated health status perception (Short Form (SF)-12 questionnaire) and dyspnoea (Medical Research Council scale). Among 5,314 subjects, 759 (362 females) had COPD and 4,555 (2,850 females) did not. In general, females reported more dyspnoea and physical limitation than males. 54% of females without COPD reported a dyspnoea score ≥ 2 versus 35% of males. A similar trend was observed in females with COPD (63% versus 44%). In the entire study population, female sex was a factor explaining dyspnoea (OR 1.60, 95%CI 1.40-1.84) and SF-12 physical score (OR -1.13, 95%CI -1.56- -0.71). 40% of females versus 28% of males without COPD reported their general health status as fair-to-poor. Females with COPD showed a similar trend (41% versus 34%). Distribution of COPD severity was similar between sexes, but currently smoking females had more severe COPD than currently smoking males. There are important sex differences in the impact that COPD has on the perception of dyspnoea, health status and physical activity limitation.

Value of biologic therapy: a forecasting model in three disease areas.

OBJECTIVE: Forecast the return on investment (ROI) for advances in biologic therapies in years 2015 and 2030, based upon impact on disease prevalence, morbidity, and mortality for asthma, diabetes, and colorectal cancer. METHODS: A deterministic, spreadsheet-based, forecasting model was developed based on trends in demographics and disease epidemiology. 'Return' was defined as reductions in disease burden (prevalence, morbidity, mortality) translated into monetary terms; 'investment' was defined as the incremental costs of biologic therapy advances. Data on disease prevalence, morbidity, mortality, and associated costs were obtained from government survey statistics or published literature. Expected impact of advances in biologic therapies was based on expert opinion. Gains in quality-adjusted life years (QALYs) were valued at $100,000 per QALY. RESULTS: The base case analysis, in which reductions in disease prevalence and mortality predicted by the expert panel are not considered, shows the resulting ROIs remain positive for asthma and diabetes but fall below $1 for colorectal cancer. Analysis involving expert panel predictions indicated positive ROI results for all three diseases at both time points, ranging from $207 for each incremental dollar spent on biologic therapies to treat asthma in 2030, to $4 for each incremental dollar spent on biologic therapies to treat colorectal cancer in 2015. If QALYs are not considered, the resulting ROIs remain positive for all three diseases at both time points. CONCLUSIONS: Society may expect substantial returns from investments in innovative biologic therapies. These benefits are most likely to be realized in an environment of appropriate use of new molecules. LIMITATIONS: The potential variance between forecasted (from expert opinion) and actual future health outcomes could be significant. Similarly, the forecasted growth in use of biologic therapies relied upon unvalidated market forecasts.

Evaluating the adequacy of disease control in patients with rheumatoid arthritis: a RAND appropriateness panel.

OBJECTIVES: There is a lack of agreement on assessing disease activity in patients with RA and determining when the RA treatment should be changed or continued. A panel of rheumatologists was convened to develop guidelines to assess adequacy of disease control, focusing on the use of disease-modifying anti-rheumatic drugs. METHODS: The Research and Development/University of California in Los Angeles (RAND/UCLA) Appropriateness Method was used to evaluate disease control adequacy. After a literature review, 108 scenarios were developed to simulate situations most likely to be encountered in clinical practice and rated on a 9-point scale by a 10-member expert panel. RESULTS: Final appropriateness rankings for the scenarios were as follows: 37% 'appropriate', 48% 'inappropriate', and 16% 'neutral'. The panelists felt that patients with disease control in the 'appropriate' range have adequate control with their current therapy, whereas those in the 'inappropriate' range should be considered for a change in therapy. Those in 'neutral' areas should have their therapy reviewed carefully. The panelists recommended that the clinically active joint count should be considered the most important decision factor. In patients with no clinically active joints, regardless of other factors no change in therapy was felt to be warranted. Patients with five or more active joints should be considered inadequately treated, and in patients with one to four active joints other variables must be considered in the decision to change therapy. CONCLUSION: These preliminary guidelines will assist the clinician in determining when a patient's clinical situation warrants therapy escalation and when continuing the current regimen would be appropriate.

Systematic review and meta-analysis of real-world adherence to drug therapy for osteoporosis.

OBJECTIVE: To quantify the adherence of patients to drug therapy for osteoporosis in real-world settings via a systematic review and meta-analysis of observational studies. METHODS: The PubMed and Cochrane databases were searched for English-language observational studies published from January 1, 1990, to February 15, 2006, that assessed patient adherence to drug therapy for osteoporosis using the following medical subject headings and keywords: drug therapy, medication adherence, medication persistence, medication possession ratio, patient compliance, and osteoporosis. Studies were stratified into 3 groups: persistence (how long a patient continues therapy), compliance (how correctly, in terms of dose and frequency, a patient takes the medication), and adherence (a combination of persistence and compliance). A random-effects model was used to pool results from the selected studies. RESULTS: Twenty-four studies were included in the meta-analysis. The pooled database-derived persistence rate was 52% (95% confidence interval [CI], 44%-59%) for treatment lasting 1 to 6 months, 50% (95% CI, 37%-63%) for treatment lasting 7 to 12 months, 42% (95% CI, 20%-68%) for treatment lasting 13 to 24 months, returning to 52% (95% CI, 45%-58%) for treatment lasting more than 24 months. Pooled adherence rates decreased from 53% (95% CI, 52%-54%) for treatment lasting 1 to 6 months to 43% for treatment lasting 7 to 12 months (95% CI, 38%-49%) or 13 to 24 months (43%; 95% CI, 32%-54%). The pooled refill compliance estimate was 68% (95% CI, 63%-72%) for treatment lasting 7 to 12 months and 68% (95% CI, 67%-69%) for treatment lasting 13 to 24 months. The pooled self-reported compliance rate was 62% (95% CI, 48%-75%) for treatment lasting 1 to 6 months and 66% (95% CI, 45%-81%) for treatment lasting 7 to 12 months. CONCLUSION: One-third to half of patients do not take their medication as directed. Nonadherence occurs shortly after treatment initiation. Terms and definitions need to be standardized to permit comparability of technologies designed to improve patient adherence. Prospective trials are needed to assess the relationship between adherence and patient outcomes.

Scoring system and clinical application of COPD diagnostic questionnaires.

OBJECTIVES: In most primary care settings, spirometric screening of all patients at risk is not practical. In prior work, we developed questionnaires to help identify COPD in two risk groups: (1) persons with a positive smoking history but no history of obstructive lung disease (case finding), and (2) patients with prior evidence of obstructive lung disease (differential diagnosis). For these questionnaires, we now present a scoring system for use in primary care. METHODS: Scores for individual questions were based on the regression coefficients from logistic regression models using a spirometry-based diagnosis of obstruction as the reference outcome. Receiver operator characteristic analysis was used to determine performance characteristics for each questionnaire. Several simplified scoring systems were developed and tested. RESULTS: For both scenarios, we created a scoring system with two cut points intended to place subjects within one of three zones: persons with a high likelihood of having obstruction (high predictive value of a positive test result); persons with a low likelihood of obstruction (high predictive value of a negative test result); and an intermediate zone. Using these scoring systems, we achieved sensitivities of 54 to 82%, specificities of 58 to 88%, positive predictive values of 30 to 78%, and negative predictive values of 71 to 93%. CONCLUSIONS: These questionnaires can be used to help identify persons likely to have COPD among specific risk groups. The use of a simplified scoring system makes these tools beneficial in the primary care setting. Used in conjunction with spirometry, these tools can help improve the efficiency and accuracy of COPD diagnosis in primary care.

Global burden of COPD: systematic review and meta-analysis.

The aim of this study was to quantify the global prevalence of chronic obstructive pulmonary disease (COPD) by means of a systematic review and random effects meta-analysis. PubMed was searched for population-based prevalence estimates published during the period 1990-2004. Articles were included if they: 1) provided total population or sex-specific estimates for COPD, chronic bronchitis and/or emphysema; and 2) gave method details sufficiently clearly to establish the sampling strategy, approach to diagnosis and diagnostic criteria. Of 67 accepted articles, 62 unique entries yielded 101 overall prevalence estimates from 28 different counties. The pooled prevalence of COPD was 7.6% from 37 studies, of chronic bronchitis alone (38 studies) was 6.4% and of emphysema alone (eight studies) was 1.8%. The pooled prevalence from 26 spirometric estimates was 8.9%. The most common spirometric definitions used were those of the Global Initiative for Chronic Obstructive Lung Disease (13 estimates). There was significant heterogeneity, which was incompletely explained by subgroup analysis (e.g. age and smoking status). The prevalence of physiologically defined chronic obstructive pulmonary disease in adults aged > or =40 yrs is approximately 9-10%. There are important regional gaps, and methodological differences hinder interpretation of the available data. The efforts of the Global Initiative for Chronic Obstructive Lung Disease and similar groups should help to standardise chronic obstructive pulmonary disease prevalence measurement.

Misdiagnosis of COPD and asthma in primary care patients 40 years of age and over.

Chronic obstructive pulmonary disease (COPD) is often misdiagnosed as asthma, leading to inappropriate treatment and suboptimal patient outcomes. As part of a prospective study of patients with a history consistent with obstructive lung disease, we compared prior diagnostic labels with a study diagnosis based on spirometric results. We enrolled persons 40 years of age or older with prior diagnoses or medications consistent with obstructive lung disease. Patients were recruited via random mailing to primary care practices in Aberdeen, Scotland, and Denver, Colorado. Prior diagnoses of chronic bronchitis or emphysema (CBE) and asthma were reported by the subjects. Participants underwent pre- and post-bronchodilator spirometry. A study diagnosis of COPD was defined using post-bronchodilator forced expiratory volume in 1 second/forced vital capacity (FEV(1)/FVC) < 0.70. Spirometric examination was complete in 597 patients, of whom 235 (39.4%) had a study diagnosis of COPD. Among subjects with a spirometry-based study diagnosis of COPD, 121 (51.5%) reported a prior diagnosis of asthma without concurrent CBE diagnosis, 89 (37.9%) reported a prior diagnosis of CBE, and 25 (10.6%) reported no prior diagnosis of obstructive lung disease. Despite the availability of consensus guideline diagnostic recommendations, diagnostic confusion between COPD and asthma appears common. Increased awareness of the differences between the two conditions is needed to promote optimal patient management and treatment.

Symptom-based questionnaire for differentiating COPD and asthma.

BACKGROUND: Many patients with obstructive lung disease (OLD) carry an inaccurate diagnostic label. Symptom-based questionnaires could identify persons likely to need spirometry. OBJECTIVES: We prospectively tested questions derived from a comprehensive literature review and an international Delphi panel to help identify chronic OLD (COPD) in persons with prior evidence of OLD. METHODS: Subjects were recruited via random mailing to primary-care practices in Aberdeen, Scotland, and Denver, Colorado. Persons aged 40 and older reporting any prior diagnosis of OLD or any respiratory medications in the past year were enrolled. Participants answered 54 questions covering demographics and symptoms and underwent spirometry with reversibility testing. A study diagnosis of COPD was defined by fixed airway obstruction as measured by post-bronchodilator FEV(1)/FVC <0.70. We examined ability of individual questions in a multivariate framework to discriminate between persons with and without the study diagnosis of COPD. RESULTS: 597 persons completed all investigations and proceeded to analysis. The list of 54 questions yielded 52 items for analyses, which was reduced to 19 items for entry into a multivariate regression model. Nine items had significant relationships with the study diagnosis of COPD, including increased age, pack-years, worsening cough, breathing-related disability or hospitalization, worsening dyspnea, phlegm quantity, cold going to the chest, and receipt of treatment for breathing. Individual items yielded odds ratios ranging from 0.33 to 20.7. This questionnaire demonstrated a sensitivity of 72.0 and a specificity of 82.7. CONCLUSIONS: A short, symptom-based questionnaire identifies persons more likely to have COPD among persons with prior evidence of OLD.

Symptom-based questionnaire for identifying COPD in smokers.

BACKGROUND: Symptom-based questionnaires may enhance chronic obstructive pulmonary disease (COPD) screening in primary care. OBJECTIVES: We prospectively tested questions to help identify COPD among smokers without prior history of lung disease. METHODS: Subjects were recruited via random mailing to primary care practices in Aberdeen, UK, and Denver, Colo., USA. Current and former smokers aged 40 or older with no prior respiratory diagnosis and no respiratory medications in the past year were enrolled. Participants answered questions covering demographics and symptoms and then underwent spirometry with reversibility testing. A study diagnosis of COPD was defined as fixed airway obstruction as measured by post-bronchodilator FEV(1)/FVC <0.70. We examined the ability of individual questions in a multivariate framework to correctly discriminate between persons with and without COPD. RESULTS: 818 subjects completed all investigations and proceeded to analysis. The list of 54 questions yielded 52 items for analysis, which was reduced to 17 items for entry into multivariate regression. Eight items had significant relationships with the study diagnosis of COPD, including age, pack-years, body mass index, weather-affected cough, phlegm without a cold, morning phlegm, wheeze frequency, and history of any allergies. Individual items yielded odds ratios ranging from 0.23 to 12. This questionnaire demonstrated a sensitivity of 80.4 and specificity of 72.0. CONCLUSIONS: A simple patient self-administered questionnaire can be used to identify patients with a high likelihood of having COPD, for whom spirometric testing is particularly important. Implementation of this questionnaire could enhance the efficiency and diagnostic accuracy of current screening efforts.

Airway obstruction in never smokers: results from the Third National Health and Nutrition Examination Survey.

PURPOSE: Chronic obstructive pulmonary disease (COPD) is usually described as a disease of cigarette smoking. COPD is rarely considered in persons with no smoking history except in the context of another exposure. Accordingly, the disease has not been well characterized in these "never smokers." METHODS: We evaluated airway obstruction (defined as forced expiratory volume in 1 second/forced vital capacity <0.70) in US adults aged 30 to 80 years interviewed in the Third National Health and Nutrition Examination Survey with valid spirometry who had never smoked. Previously described risk factors were examined for their association with obstruction in bivariate and multivariate analyses. RESULTS: Never smokers represented 42% of the Third National Health and Nutrition Examination Survey population aged 30 to 80 years, with obstruction prevalence of 91 per 1000. Never smokers accounted for 4.56 million cases of obstruction, or 23% of the total burden. Among these obstructed never smokers, 19% reported a prior diagnosis of asthma alone, and 12.5% reported COPD (alone or with asthma), leaving 68.5% with no prior respiratory diagnosis. After adjustment for other factors, higher rates of obstruction were significantly associated with increasing age, male sex, lower body mass index, and a history of allergies. CONCLUSIONS: Never smokers represent a significant proportion of airway obstruction in US adults. Only one fifth of obstruction in this group is explained by asthma. COPD may explain much of the remainder, although known risk factors were not explanatory in this dataset. Recommendations that lung health screening programs be limited to smokers should be reconsidered.

Chronic obstructive pulmonary disease in patients under age 65: utilization and costs from a managed care sample.

OBJECTIVES: Chronic obstructive pulmonary disease (COPD) affects all adult age groups, not just elderly males. We assessed the health care utilization and cost impact of COPD in different age groups. METHODS: We compared burden of illness, utilization, and charges for younger versus older COPD patients and versus age- and gender-matched controls. RESULTS: A total of 16.9% of patients with COPD were under age 65. Patients with COPD (n=19,338) had higher comorbidity than age-matched controls (n=94,384) across all age groups. Younger patients with COPD had lower comorbidity scores and fewer hospitalizations but more COPD-related emergency services than older patients with COPD. Average COPD-related charges were higher for younger patients. Facility-based care was the cost driver across all age groups. CONCLUSIONS: COPD is a burden to younger individuals in the workforce, who are likely to be enrolled in a commercial health plan.

Improving the management of chronic obstructive pulmonary disease.

As the fourth leading cause of death in the United States, chronic obstructive pulmonary disease (COPD) represents a major burden to the healthcare system and society at large. Underdiagnosis and undertreatment lead to an increased economic burden, with exacerbations being a key driver of costs. COPD symptoms compromise quality of life (QOL), which affects both patients and caregivers. Appropriate management decreases healthcare utiization and improves QOL. This article provides an overview of COPD and promotes understanding of opportunities to optimize patient health and outcomes for those with the disease. Specific interventions that have been demonstrated to improve clinical and economic outcomes for COPD include improved implementation of guidelines, optimized pharmacologic treatment, and risk-factor reduction.

Questions for COPD diagnostic screening in a primary care setting.

OBJECTIVES: To test questions usable in an ambulatory clinic to identify persons likely to have chronic obstructive pulmonary disease (COPD). METHODS: Analyses were performed as part of a study to identify patients with likely COPD in the Glenfield UK primary care clinic. Patients age 40 and older were recruited based on one of the following criteria: (1) respiratory medications in previous 2 years; (2) history of smoking or (3) history of asthma with no current medications based on case notes. Consenting patients reported smoking history, symptoms, and personal and family history of respiratory conditions. Spirometry with reversibility was conducted to ATS standards. Analyses were performed on this database to test questions for identifying patients with COPD from a sample of patients with a positive smoking history. Multivariate logistic regression identified the question set that best discriminated COPD from other conditions using receiver operating characteristic curves. The usefulness of a simple scoring system was assessed. RESULTS: The study sample included 369 current and former smokers. Patients were diagnosed as: COPD=62 (16.8%); asthma=30 (8.1%); or no obstructive lung disease=277 (75.1%). The best questions for discriminating between persons with and without COPD included items on age, dyspnoea on exertion, and wheeze. This set of questions identified COPD patients with a sensitivity of 77.4--87.1% and specificity of 71.3--76.2%. CONCLUSIONS: A simple questionnaire can facilitate the diagnosis of COPD in a primary care setting.

Development of a population-based screening questionnaire for COPD.

COPD is commonly under-diagnosed, in part because people at risk are unaware of the relevant risk factors and do not recognize related symptoms. Providing this information might permit earlier disease identification but the questions chosen should identify those with spirometrically defined airflow obstruction. Using a population-based data set, we have determined which questions identify persons most likely to have airflow obstruction. Potential questions were selected by review of COPD risk factors and clinical features. Validation was by retrospective analysis of the NHANES III data set, a population-based U.S. household survey that included spirometry. We examined the predictive ability of individual questions in a multi-variate framework to correctly discriminate between persons with and without spirometric airway obstruction (defined as FEV1/FVC < 0.70). We then tested the discriminatory ability of the questions in combination. The following items showed significant predictive ability: increased age, smoking status, pack-years, cough, wheeze, and prior diagnosis of asthma or COPD. The best performing combination was age, smoking status, pack-years smoked, wheeze, phlegm, body mass index, and prior diagnosis of obstructive lung disease. Using this combination in a population of current and former smokers aged 40 and over, we achieved a sensitivity of 85% and specificity of 45%, with a positive predictive value of 38% and a negative predictive value of 88%. Performance of this tool is comparable to other screening methods designed for use in a general population. Symptom-based questionnaires can be a viable method to identify persons likely to have COPD in the general population. Dissemination of such tools should raise awareness among at-risk persons and help identify COPD patients in the primary care setting.

The cost of chronic obstructive pulmonary disease and its effects on managed care.

Chronic obstructive pulmonary disease (COPD) designates respiratory disorders characterized by airway obstruction that is not fully reversible. An estimated 10 million adult Americans have COPD, and the prevalence is rising. Direct and indirect costs of managing COPD exceed dollars 32 billion annually, and this health care burden has provoked vigorous efforts by major public health organizations to evaluate and improve quality of care for COPD. The authors review the substantial effects of COPD on managed care and discuss evidence-based strategies for its effective management.

Coordinated diagnostic approach for adult obstructive lung disease in primary care.

AIMS: To present an age-stratified approach to the diagnosis of obstructive lung disease based on asthma and COPD guidelines and epidemiology. METHODS: Asthma guidelines emphasize the role of the history and physical examination, with pulmonary function used primarily to confirm the diagnosis. COPD guidelines begin with symptoms and risk exposure, presenting spirometry as the primary diagnostic maneuver. Data from the National Health Interview Survey and the Third National Health and Nutrition Examination Survey illustrate relationships in prevalence of asthma and COPD in nationally representative samples. RESULTS: Asthma prevalence in adults declines with age from 5-10% at age 20-40 to 4-8% above age 60. COPD is uncommon in adults under age 40 but increases with age, surpassing asthma in older adults. CONCLUSIONS: These trends suggest that asthma screening is most useful in adults up to age 40, after which COPD screening and differential diagnosis are of comparable or greater utility.

Determinants of quality of life changes among long-term cardiac transplant survivors: results from longitudinal data.

BACKGROUND: Cross-sectional analyses have identified significant associations between quality of life (QOL), and comorbidities and adverse effects in cardiac transplant recipients. However, little is known about factors that influence changes in QOL over time. This study examines both cross-sectional and longitudinal data from long-term survivors to identify factors that affect differences in QOL among recipients and individual changes in QOL during a 1-year period. METHODS: Self-selected enrollees completed questionnaires, including QOL scales, at 3-month intervals. Repeated measures multiple regression analysis was used to examine the association between the QOL scales and comorbidities, adverse effects, and compliance measures, controlling for other factors. RESULTS: We included 569 participants in the analysis, with a mean time since transplantation of 8.6 years. Cross-sectional results showed that the number of comorbidities, treatment non-compliance, and several adverse effects were associated with low QOL. In longitudinal results, waiting to take medications and taking less medication because of lifestyle restrictions were associated with decreases in QOL over time. Hair loss, changes in face shape, and decreased sexual interest or ability also had the largest adverse effects on changes in QOL. CONCLUSIONS: These findings provide new opportunities for interventions to address factors related to decreases in QOL. Clinicians should actively solicit information about compliance with medication regimens. In addition, information about the adverse effects of medications should be considered when making therapeutic decisions.

Population impact of different definitions of airway obstruction.

There is currently no consensus on the criteria for diagnosing chronic obstructive pulmonary disease. This study evaluated the impact of different definitions of airway obstruction on the estimated prevalence of obstruction in a population-based sample. Using the Third National Health and Nutrition Examination Survey, obstructive airway disease was defined using the following criteria: 1) self-reported diagnosis of chronic bronchitis or emphysema; 2) forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) <0.70 and FEV1 <80% predicted (Global Initiative for Chronic Obstructive Lung Disease (GOLD) Stage IIA); 3) FEV1/FVC below the lower limit of normal; 4) FEV1/FVC <88% pred in males and <89% pred in females; 5) FEV1/FVC <0.70 ("fixed ratio"). Spirometry in this dataset did not include reversibility testing, making it impossible to distinguish reversible from irreversible obstruction. Rates in adults varied from 77 per 1,000 (self-report) to 168 per 1,000 (fixed ratio). For persons aged >50 yrs, the fixed ratio criteria produced the highest rate estimates. For all subgroups tested, the GOLD Stage II criteria produced lower estimates than other spirometry-based definitions. Different definitions of obstruction may produce prevalence estimates that vary by >200%. International opinion leaders should agree upon a clear definition of chronic obstructive pulmonary disease that can serve as a population-based measurement criterion as well as a guide to clinicians.

Interpreting COPD prevalence estimates: what is the true burden of disease?

STUDY OBJECTIVES: To summarize the available data on COPD prevalence and assess reasons for conflicting prevalence estimates in the published literature. DESIGN: We reviewed published studies that (1) estimated COPD prevalence for a population, and (2) clearly described the methods used to obtain the estimates. RESULTS: Thirty-two sources of COPD prevalence rates, representing 17 countries and eight World Health Organization-classified regions, were identified and reviewed. Prevalence estimates were based on spirometry (11 studies), respiratory symptoms (14 studies), patient-reported disease (10 studies), or expert opinion. Reported prevalence ranged from 0.23 to 18.3%. The lowest prevalence rates (0.2 to 2.5%) were based on expert opinion. Sixteen studies had measured rates that could reasonably be extrapolated to an entire region or country. All were for Europe or North America, and most fell between 4% and 10%. CONCLUSIONS: There is considerable variation in the reported prevalence of COPD. The overall prevalence in adults appears to lie between 4% and 10% in countries where it has been rigorously measured. Some of the variation attributed to differences in risk exposure or population characteristics may be influenced by the methods and definitions used to measure disease. Spirometry is least influenced by local diagnostic practice, but it is subject to variation based on the lung function parameters selected to define COPD.