Context:

Chronic Obstructive Pulmonary Disease (COPD) is a leading cause of morbidity and mortality. COPD is diagnosed in symptomatic individuals through spirometric testing demonstrating irreversible airflow obstruction. Spirometry in primary care settings for case-finding, diagnosis, and management in all adults with persistent respiratory symptoms or having a history of exposure to pulmonary risk factors is controversial.

Objectives:

Conduct a systematic review to determine: 1) the prevalence of COPD and airflow obstruction; 2) if spirometry improves smoking cessation; 3) if effectiveness of COPD therapies varies based on baseline or change in spirometric severity; and 4) whether spirometry provides independent prognostic value related to pulmonary outcomes.

Data Sources:

Articles published in English from 1966 to May 2005 were identified by searching MEDLINE® and the Cochrane Database. Children and individuals with asthma or alpha-1 antitrypsin disease were excluded.

Study Selection:

Ten cohort studies were included for prevalence; seven randomized clinical trials (RCTs) for smoking cessation; 53 RCTs and six meta-analyses for therapies; and five cohort studies for prognosis.

Data Extraction:

Study and patient characteristics and outcomes were abstracted. Main outcomes according to age, race, gender, and spirometric, smoking, or symptom status by question were: 1) prevalence of airflow obstruction and clinical diagnosis of COPD; 2) smoking abstinence rates; 3) exacerbation rates, hospitalizations, mortality and respiratory health status; and 4) spirometry as an independent predictor of future COPD stage and symptoms.

Data Synthesis:

Prevalence and severity of airflow obstruction, respiratory symptoms, and clinical diagnosis of COPD vary according to definition, country, and populations. Applying recent diagnostic criteria to a nationally representative U.S. survey, 7.2 percent were categorized as “at risk,” 7.2 percent had mild airflow obstruction, 5.4 percent had moderate obstruction, and 1.5 percent had severe to very severe airflow obstruction. Airflow obstruction prevalence was higher in current or past smokers and older individuals. Symptoms were associated with severity of airflow obstruction, but one-third of individuals with normal airflow reported respiratory symptoms and 21 percent with severe to very severe airflow obstruction did not report respiratory symptoms. In this survey, more than 80 percent of adults reporting a clinical diagnosis of chronic bronchitis or emphysema did not have current airflow obstruction or spirometry. Evidence regarding the effect of spirometry on smoking cessation was limited and flawed. Data indicate that spirometry is of limited use in predicting a patient's future likelihood of quitting. Seven randomized studies assessed the effect of spirometry alone or with other interventions on smoking cessation. The only study designed to evaluate the independent effect of spirometry in conjunction with clinical counseling found a 1 percent greater quit rate at 12 months in the group assigned to receive spirometry plus repeat smoking cessation counseling. Spirometry is useful in adults with bothersome respiratory symptoms for determining at what threshold of airflow obstruction initiation of therapy is likely to be beneficial. COPD treatment trials evaluated inhaled medications, pulmonary rehabilitation, disease management, supplemental oxygen, or surgery. Most were less than 1 year in duration and involved subjects with severe to very-severe airflow obstruction and frequent COPD exacerbations. Treatments reduced the percentage of subjects having one or more exacerbations by an absolute reduction of 5–6 percent but did not reduce mortality (except for oxygen in a small subset of individuals). The average magnitude of improvement for respiratory and dyspnea functional status measures was less than considered clinically significant though some subjects may notice considerable improvement.

Five large studies of greater than 1 year duration found little to no improvement in symptoms with inhaled medications among subjects with mild to moderate airflow obstruction, many of whom had respiratory symptoms and were detected based on spirometry. Analysis of one of these studies that included individuals who reported no respiratory symptoms showed that ipratropium did not prevent development of symptoms at 3 years of followup. Studies have not examined the value of spirometry to monitor need for additional therapy or to identify candidates for treatment among patients who do not report symptoms. However, it is unlikely to be effective because effectiveness of inhaled interventions are comparable, spirometry is not a useful guide for selecting among inhaled therapies, higher doses of inhaled interventions or combination therapies were not more effective than lower doses or monotherapy, clinical improvement was not associated with an individual's spirometric response to therapy, treatments other than smoking cessation did not alter spirometric decline, and interventions did not prevent symptom development in asymptomatic individuals. We estimated that the costs of routine spirometry of all adult smokers, ex-smokers, and non-smokers with any respiratory symptom would exceed $1 billion. Based on the prevalence of respiratory symptoms, levels of airflow obstruction identified in the U.S., and the effectiveness of drug therapy, we estimated that such a strategy applied to a clinic population of 10,000 adults would identify 6,588 for spirometric testing, detect 129 (1.3 percent) who would be candidates for COPD therapy, and result in 8 who would benefit from reduction in exacerbations. On average, respiratory status measures and survival would not be improved. Hospitalizations were rarely reported but the absolute reduction was 4–7 percent. If subjects with moderate airflow obstruction (FEV₁ between 50–80 percent predicted) are assumed to benefit, then 529 (5.3 percent) adults would be treatment candidates and 32 (0.3 percent) would benefit. These benefits would be retained at reduced costs and testing if spirometry was targeted to adults reporting bothersome symptoms. Spirometry provides independent prognostic value regarding morbidity and mortality. Subjects with chronic sputum production and normal spirometry are not at increased risk for developing airflow obstruction, and more than half of these subjects do not have chronic sputum production after 10 years of followup.

Conclusions:

Spirometry, in addition to clinical examination, improves COPD diagnostic accuracy compared to clinical examination alone and it is a useful diagnostic tool in individuals with symptoms suggestive of possible COPD. The primary benefit of spirometry is to identify individuals who might benefit from pharmacologic treatment in order to improve exacerbations. These include adults with symptomatic, severe to very severe airflow obstruction. Spirometry for case finding among all adults with persistent respiratory symptoms or those with a history of exposure to pulmonary risk factors as well as for monitoring individuals or adjusting treatment is unlikely to be beneficial unless future studies establish that spirometry improves smoking cessation rates, treatments other than smoking cessation benefit individuals with airflow obstruction who do not report respiratory symptoms, or that relative effectiveness between therapies varies according to an individual's baseline or followup spirometry. Widespread spirometric testing is likely to label a large number of individuals (many who do not report respiratory symptoms) with disease and result in considerable testing and treatment costs and health-care resource utilization.