Abstract
Introduction: In 2011, the Centers for Disease Control and Prevention for the first time ever collected nationally representative prevalence data on chronic obstructive pulmonary disease (COPD), spirometry diagnosis, and healthcare utilization factors related to COPD. This research reports on that data and describes characteristics of adults with COPD who reported diagnosis by spirometry compared to those who did not report diagnosis by spirometry. Variables examined included basic elements of healthcare utilization such as emergency room visits, hospitalization or personal physician utilization. Methods: This is a cross-sectional study using novel data from the 2011 Behavioral Risk Factor Surveillance System COPD Module. Weighted multivariable logistic regression examined factors associated with (n = 13,484) and without spirometry (n = 3,131). Results: Spirometry to diagnose COPD was reported by 78% of adults and increased with age. In multivariable modeling, spirometry was more likely in: Black, non-Hispanic compared to white non-Hispanic; current and former compared to never smokers; adults with co-morbidity including asthma, depression, and cardiovascular disease; adults with a doctor; and those who had been to emergency room/hospital for COPD. Those less likely to receive a spirometry were: Hispanic and reported exercise in the past 30 days. Conclusions: This study identified that adults diagnosed with COPD without a spirometry tended to be Hispanic, younger, healthier, and had less utilization of medical resources. This study is a first step in understanding the potential impact of COPD diagnosis made without spirometry.
Introduction
In 2011, the Centers for Disease Control and Prevention introduced a survey module in the Behavioral Risk Factor Surveillance System (BRFSS) on chronic obstructive pulmonary disease (COPD), use of spirometry to diagnose COPD, and healthcare utilization factors related to COPD. This module is in addition to the standard core BRFSS questions that include sociodemographic factors, health behaviors, and health outcomes, among others. Given that COPD will be the 3rd and 5th leading cause of mortality and disability by 2020 (Citation1, 2) this new data is timely and permits an understanding of the burden of COPD on the individual and the healthcare system. It also allows researchers an initial look at the use of spirometry in COPD diagnosis in a nationally representative sample. With additional administration of the module, this new data will permit a description over time in COPD trends. Therefore, the aim of this study was to describe characteristics of adults with COPD, including sociodemographic factors and co-morbidity, and healthcare utilization such as emergency room visits, hospitalization, or personal physician utilization. These factors were examined in adults who reported diagnosis by spirometry compared to those who did not report diagnosis by spirometry.
Methods
This research involved the analyses of existing data and was deemed minimal risk, exempt status under federal regulation 45 CFR 46.101(b) by the Institutional Review Board at Kent State University (Protocol #12-328).
The BRFSS is a federally-funded telephone survey conducted annually by the Centers for Disease Control and Prevention with the state health departments and those in Washington, DC; Puerto Rico; the U.S. Virgin Islands; and Guam (Citation3). BRFSS uses a multistage cluster design and random digit dialing to select a representative sample of civilian, non-institutionalized adults aged ≥18. The data from each state are weighted to reflect the respondent's probability of selection and the age-by-sex or age-by-race/ethnicity-by-sex category in the population of the state. A detailed description of the survey methods has been published elsewhere (Citation4). The 2011 BRFSS used new methodology that included the addition of cell-phone-only respondents to improve representation of the population. The median response rate was 53% for landline respondents consistent with previous administrations, and 28% for cell-phone-only respondents, with a 77% cooperation rate for each method.
Clinician diagnosed COPD was determined from the question: “Has a doctor, nurse, or other health professional EVER told you that you have (COPD) chronic obstructive pulmonary disease, emphysema, or chronic bronchitis?” If a respondent answered “yes,” they had been told they have COPD; they received the novel optional COPD module if they resided in one of 21 states, Washington DC, or Puerto Rico. The analyses for this study are limited to the responses from the optional module (n = 21,567).
Outcome of Interest: Spirometry
Spirometry was determined by the question: “Earlier you said that you had been diagnosed with chronic obstructive pulmonary disease (COPD)…have you ever been given a breathing test to diagnose your COPD, chronic bronchitis, or emphysema?” Breathing test was a proxy as spirometry was not used in the BRFSS. Respondents were excluded if they reported “don't know/not sure” or “refused” to the breathing test question (n = 764).
To examine predictors associated with spirometry to diagnose COPD, the following covariates were included in analyses: Asthma; depression; angina/coronary heart disease/myocardial infarction; any exercise in past 30 days; smoking status; personal doctor; health care coverage; seen a doctor about shortness of breath; been to the emergency room/hospital for shortness of breath; and demographic variables including: Gender; age; race/ethnicity; marital status; education; and income. Respondents were excluded who had missing data on any covariate. The final sample size with complete data was n = 16,615.
Statistical analysis
Sampling weights that adjust for unequal selection probabilities, survey non-response, and oversampling were used to account for the complex sampling design. Weighted prevalence estimates, weighted mean estimates, and corresponding 95% confidence intervals (CI), were computed for the outcome and all covariates. In bivariate analyses covariates were examined using Chi-square for discrete or Student's t-test for continuous variables to describe the characteristics of adults diagnosed versus not diagnosed by spirometry. Logistic regression was used in univariate analyses to determine the weighted prevalence odds ratios and 95% CI for each covariate with spirometry. Covariates significant at p ≤ 0.05 were retained for multivariable logistic regression. All covariates were then maintained in a full model to describe the characteristics of those diagnosed and not diagnosed by spirometry. Analyses were conducted in SAS 9.2 (SAS Institute Inc., Cary, NC, USA) using survey procedures (PROC SURVEYMEANS, PROC SURVEYFREQ, AND PROC SURVEYLOGISTIC) to obtain correct variance estimates, using Taylor series linearization method (Citation5).
Results
Overall, 78% of adults with COPD reported their COPD was diagnosed by spirometry (Table ). The sample was predominately female and white non-Hispanic, with an average age of 56. The majority of respondents were high school graduates or less with household income <$50,000. Thirty-nine percent were current and 37% were former smokers. The co-morbidity burden consisted of 46% with asthma, 38% with depression, and 24% with angina/coronary heart disease/myocardial infarction. The majority had a personal doctor and healthcare coverage. Healthcare utilization in the past 12 months included: 43% who had seen a doctor for shortness of breath and 17% who had been to the emergency room or were hospitalized for COPD.
Table 1. Demographic Characteristics, Health and Health Utilization Factors of Respondents with Chronic Obstructive Pulmonary Disease in the BRFSS 2011, n = 16,615
In bivariate analyses, those without spirometry were younger and a higher proportion was Hispanic (Table ). Those without spirometry were more likely to be healthier overall as evidenced by a higher proportion reporting any exercise in the past 30 days and lower prevalence of: Depression; asthma; angina/coronary heart disease/myocardial infarction; doctor visits for shortness of breath; and visits to the emergency room/hospital for COPD. Those without spirometry had a higher prevalence of current smoking and never smoking, and a lower prevalence of being former smokers.
Table 2. Health Factors and Demographic Characteristics of Respondents with Chronic Obstructive Pulmonary Disease by diagnostic breathing test in the BRFSS 2011, n = 16,615
In weighted, unadjusted analyses, all variables were significant and retained for multivariable modeling except gender, education, and income (Table ). In weighted, adjusted analysis, age and race were the only significant sociodemographic factors: Black non-Hispanic had a 2.4 (CI: 1.5, 3.8) times increased odds of having received spirometry while Hispanics had a 60% (CI: 0.28, 0.58) reduced odds of having had spirometry compared to white, non-Hispanic. Current and former compared to never smokers had a 1.4 (CI: 1.1, 1.8) and 1.4 (CI: 1.1, 1.9) times increased odds of having had spirometry. Those who reported any exercise in the past 30 days compared to those who did not had a 19% (0.67, 0.98) reduced odds of having had spirometry.
Table 3. Unadjusted and adjusted weighted prevalence odds ratios and 95% confidence intervals for breathing test to diagnose COPD among persons with COPD in the 2011 BRFSS, n = 16,615
Examining co-morbidities, adults with asthma when compared to those without asthma had 2.6 (CI: 2.1, 3.2) times, those with a depressive disorder compared to those without had 1.3 (1.1, 1.6) times, and persons with angina/coronary heart disease/myocardial infarction when compared to those without had 1.6 (CI: 1.3, 2.1) times increased odds of having received spirometry to diagnose COPD. Persons with a personal doctor compared to those without had 1.8 (CI: 1.3, 2.5) times and persons who had been to emergency room/hospital for COPD compared to those who had not had a 1.3 (CI: 1.1, 1.7) times increased odds of having had spirometry.
Discussion
Although not as large as in some studies, the percentage of adults diagnosed with COPD in the absence of spirometry remains significant. The adults in the current research diagnosed with COPD without spirometry had greater odds of being younger; Hispanic; and current smokers. They also had reduced odds of having a personal doctor but greater odds of being healthier as evidenced by: Reporting any exercise in the past 30 days, less co-morbidity burden, and not having seen a doctor for shortness of breath. These respondents appear to have been diagnosed with COPD by other means such as history and physical which has been shown to be less valid (Citation6, 7).
There are potential limitations in this study, requiring careful interpretation of the results. These limitations are inherent in the cross-sectional design and use of self-reported survey data and include: Potential for inaccurate or incomplete recall of COPD diagnosis and receipt of spirometry, lack of confirmation of spirometry diagnosis and appropriateness of spirometry interpretation, and timing of the spirometry test (i.e., performed as diagnostic test or subsequent to diagnosis). Another potential limitation is that some of these individuals who reported COPD may have actually been diagnosed with asthma, particularly if they are in the younger age groups. While this could not be explored in the current study, recommendations are that asthma be diagnosed by spirometry. There were a seemingly high proportion of respondents who reported concurrent COPD and asthma; however, there is a wide range in the literature on the prevalence of concurrent disease with estimates showing between 10 to 33% of patients with COPD also having asthma (Citation8–10).
A random sample in an Italian population that was administered a self-report survey demonstrated concurrent disease in those age 20–44, 45–64, and 65–84 of 33%, 27%, and 25% (Citation11). COPD is often misdiagnosed as asthma in younger adults and asthma is often misdiagnosed as COPD in older adults. The current research suggests that the overlapping of disease may be higher than anticipated and that additional research on the coexistence of these diseases should be considered as they are largely examined separately and in different age groups (i.e., asthma studies in children and young adults vs. COPD studies in older adults). In this particular study, we have inferred the COPD diagnosis from an affirmative answer to the survey question recapitulated in the methods section above which included chronic bronchitis.
Chronic bronchitis although precisely defined does necessarily infer spirometric obstruction and may be applied to many populations which do not have COPD. Grouping of chronic bronchitis with COPD and emphysema may have led to increased reporting to this question and an increased number in this study which may not have had obstruction and COPD. This type of information bias could be partially responsible for our significant number of self-reported patients with COPD under the age of 40, patients with COPD who were never smokers (35.1% in respondents < 40 years old; data not shown, 22% overall) and the somewhat younger mean age in our study of COPD patients of 56 years.
Nonetheless, epidemiologic research has found the prevalence of non-smoking in people with COPD to be 17–39%, consistent with our results (Citation12–15). These figures will undoubtedly vary by country and can be related to for example indoor open fire cooking in developing countries and to factors such as environmental exposures in developed countries. The United States National Health and Nutrition Examination Study III found the prevalence to be 25% and this corresponds to our findings (Citation12). The Burden of Obstructive Lung Disease (BOLD) Study which included 14 countries found that the overall prevalence of non-smoking in those with COPD was 23.3% in those with COPD stage II or greater (Citation13). Finally, the Latin American Project for the Investigation of Obstructive Pulmonary Disease (PLATINO) study found the prevalence to be 26% (Citation14). Although we clearly acknowledge these potential limitations, it is likely that our analyses are useful in the preliminary exploration of this research question given the population size and previously proven statistical validity of such an approach (Citation6, Citation16–18). This report to our knowledge is the first to describe demographic factors associated with and without spirometry use in the diagnosis of COPD using data from a nationally representative sample of adults.
Overdiagnosis and underdiagnosis of COPD result from not performing diagnostic spirometry and consequently 25 to 50% of clinically important disease is misdiagnosed (Citation7). Adults in the current research without spirometry are at risk of overdiagnosis with potential for underdiagnosis of severity. Overdiagnosis is problematic in that it may lead to inappropriate use of pharmacotherapy and can result in decreased bone mineral density, pneumonia, and cardiovascular events (Citation19–26) and it may leave another condition such as asthma undetected. Conversely, underdiagnosis of disease or severity can lead to worsening of disease and health-related quality of life, particularly in patients with moderate COPD (Citation27).
Use of appropriate medications can reduce frequency of exacerbations by up to 25% (Citation20, Citation28, Citation29). In a retrospective study of spirometry in the Department of Veterans Affairs, newly diagnosed patients who had spirometry were more likely to have medications prescribed (Citation30). Other small, clinic-based studies have shown varied results with spirometry increasing referral to a specialist but not medication use (Citation31) and increases or decreases in number and dose of medications (Citation32–34). Spirometry may be one method to support optimal management of COPD; however, population-based studies examining impact on medications, services, hospitalizations, and mortality are needed to provide supporting evidence.
The reasons for the observed high prevalence (78%) of spirometry need to be better understood. Potential explanations include that the historically low estimates (∼33%) come from smaller clinical studies that are not nationally representative estimates. Other explanations include that the current data is self-report, or because the phrase “diagnosis by a breathing test” is not “spirometry.” Another and more likely explanation is that the BRFSS is reporting cumulative prevalence of spirometry rather than administration of spirometry at diagnosis of COPD. However, the current results may also accurately represent diagnosis of COPD by spirometry. Regardless of the conflicting reports regarding diagnosis by spirometry, more attention needs to be made to how patients are being diagnosed, with spirometry being the gold standard and history and physical being an initial screening tool.
Current and former smokers were more likely to have had diagnostic spirometry compared to never smokers. Thirty-one percent of those with COPD diagnosed without spirometry in this research were never-smokers and the overall prevalence of never-smoking was 24%. While this prevalence seems high, as stated, epidemiologic research has found the prevalence of never-smoking in adults with COPD to be 17–39% (Citation12–15), comparable to our findings. These results validate the prevalence of never smoking in the current study and the current study supports that spirometry is a necessary diagnostic tool in all suspected cases of COPD regardless of smoking status.
Socioeconomic status (SES) was not associated with odds of having had spirometry. These findings suggest reasonable initial diagnostic availability regardless of SES; however, more needs to be done as SES is associated with poor health-outcomes in COPD. Although this relationship may be confounded by co-morbidity, environmental exposures, or other factors that are related to low SES (Citation35), the lowest compared to the highest SES has three times the risk for rehospitalization for COPD (Citation36), and those living in low compared to high income areas have higher readmission rates (Citation37). Given the course of disease and utilization, future research needs to consider whether the findings in the literature are signs of inadequate follow-up, access to or compliance with medications, or patient-level factors that could not be examined in the current research.
In the current research, racial/ethnic differences were observed in spirometry while in the literature, differences have been observed in COPD prevalence. White, non-Hispanic (50.8 per 1,000) followed by Black, non-Hispanic (38.6 per 1,000) have significantly higher rates of chronic bronchitis when compared to Hispanics (20.6 per 1,000) (Citation38) and a similar pattern is seen for emphysema. There are also prevalence differences within the Hispanic population with Puerto Rican respondents reporting 6.9% prevalence and Mexican Americans reporting 2.6% prevalence (Citation39). The overall prevalence of COPD appears low in Hispanics and this may contribute to the low use of spirometry or vice versa; however, the adults in the current study all have prevalent COPD and other factors may be associated with the low use of spirometry.
Low use of spirometry may be a result of ethnic/racial disparities in the healthcare system, as a recent study assessing biases among primary care physicians found substantial implicit biases toward Latinos (Citation40). These biases may affect diagnosis or treatment regimens in Hispanics/Latinos with COPD. These findings cannot be confirmed in the current research and deserve further investigation to examine outcomes and ensure that Hispanics/Latinos with COPD receive optimal clinical management.
Finally, this research observed that adults diagnosed with COPD without spirometry tended be younger and healthier whereas patients diagnosed with spirometry tended to be older with more co-morbidities and with greater healthcare utilization as assessed by emergency room and/or hospitalization and personal physician identification. Although these findings need to be interpreted within the limitations of this study as noted above, patients in these groups possessing a true diagnosis of COPD, may benefit significantly from thorough evaluation and optimal intervention.
Disease progression in COPD is likely to occur due not only to aging effects and contributory behaviors but also due to suboptimal management of disease including not having diagnostic spirometry. Over time, the no-spirometry group may begin to look more like the spirometry group becoming older, acquiring more chronic disease, and having higher healthcare utilization. This may be the case when examining the differences between those who have had and have not had spirometry (Table ). Confirmation with spirometry may lead to changes in disease management and potentially decreased disease burden (Citation32–34, Citation41, 42). It is suggested however in our analysis that lack of spirometry confirmation may not have been directly associated with healthcare utilization as measured by these simple self-reported elements at the time of survey.
Conclusions
In conclusion, adults diagnosed with COPD without spirometry were Hispanic, healthier, younger, current smokers, and had less COPD-related healthcare utilization when simply assessed by self-reported variables. This could pose issues of both over and underdiagnosis as well as setting the stage for possible unrecognized disease progression and suboptimal management and underscores the potential complexity of the relationship between the use of spirometry for COPD diagnosis and healthcare utilization. Further studies are needed to more precisely define both the magnitude and potential impact of such factors on healthcare utilization due to underutilization of spirometry in various populations.
Declaration of Interests Statement
The authors have no conflicts of interest to report.
Author contributions for Mowls, Cheruvu, Schilz, and Zullo:
has made substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data (equal contributions);
has drafted the submitted article or revised it critically for important intellectual content (equal contributions);
has provided final approval of the version to be published (equal contributions).
This work was supported by the Farris Family Innovation Award.
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