March 10, 2008 — The US Preventive Services Task Force (USPSTF) has issued recommendations summarizing the evidence for spirometry as a screening tool for chronic obstructive pulmonary disease (COPD). The new guidelines are posted in the March 3 Early Release issue of the Annals of Internal Medicine and will appear in the April 1 print issue.

"Fewer than half of the estimated 24 million Americans with airflow obstruction have received a COPD diagnosis, and diagnosis often occurs in advanced stages of the disease," write Kenneth Lin, MD, from the Agency for Healthcare Research and Quality (AHRQ), Rockville, Maryland, and colleagues from the USPSTF. "Because 4 in 5 patients with COPD are current or former smokers, some groups have advocated mass screening of asymptomatic smokers by using office spirometry. Early detection could theoretically improve health outcomes by increasing smoking cessation rates; administration of influenza and pneumococcal vaccines as top priorities; and permitting earlier initiation of pharmacologic treatments, oxygen therapy, or pulmonary rehabilitation."

The USPSTF reviewed English-language articles identified by searching PubMed and the Cochrane Library through January 2007, recent systematic reviews, expert suggestions, and reference lists from retrieved articles. Eight key questions were posed regarding benefits and harms of screening for COPD with spirometry, and specific inclusion and exclusion criteria for eligible study types were developed for each question. Studies were abstracted and rated for quality with predefined USPSTF criteria.

Although pharmacotherapy for COPD has been shown to reduce acute exacerbations in patients with severe disease, severe COPD is infrequent in the overall US population. Evidence to date has not shown that spirometry independently improves smoking cessation rates. Screening may result in potential harms such as false-positive results leading to subsequent unnecessary therapy with adverse effects.

Using data on the prevalence of airflow obstruction in the US population, the USPSTF calculated projected outcomes from screening groups based on age and smoking status. None of the reviewed studies offered direct evidence concerning health outcomes associated with COPD screening.

"Screening for COPD using spirometry is likely to identify a predominance of patients with mild to moderate airflow obstruction who would not experience additional health benefits if labeled as having COPD," the review authors write. "Hundreds of patients would need to undergo spirometry to defer a single exacerbation."

Key questions regarding the benefits and harms associated with screening for COPD with spirometry and a summary of available evidence answering these questions were as follows:

• Does screening for COPD with spirometry reduce morbidity and mortality?
  
  No published controlled studies were identified that answered this question.
  
  
• What is the prevalence of COPD in the general population, and do risk factors reliably differentiate high-risk from average-risk populations?
  
  In the general US population, approximately 1 in 14 adults has objectively measured airflow obstruction consistent with COPD, although this is underdiagnosed in primary care settings. Diagnosing COPD from symptoms alone leads to overdiagnosis in patients who do not have airflow obstruction. Although increasing age and smoking history are associated with increased risk for severe disease, these factors do not reliably discriminate between high-risk and average-risk populations.
  
  
• What are the adverse effects of screening for COPD with spirometry?
  
  To date, no evidence suggests any clinically significant adverse effects associated with spirometry, although a baseline percentage of false-positive results occur in asymptomatic healthy individuals.
  
  
• Compared with other smokers, do smokers in whom COPD is detected by screening spirometry have better rates of smoking cessation?
  
  The evidence is inconclusive that spirometry could be an independent motivational tool for smoking cessation. Limitations of most studies addressing this question include failure to evaluate spirometry independently from other therapies known to improve smoking cessation rates, sample size too small to detect a statistically significant effect, and heterogeneity of interventions and outcomes preventing meta-analysis.
  
  
• Is pharmacologic treatment, oxygen therapy, or pulmonary rehabilitation for COPD associated with decreased morbidity and mortality?
  
  In patients with symptomatic, severe COPD, pharmacologic treatments may slightly reduce exacerbations and all-cause mortality. However, the strongest evidence for reduced mortality came from a randomized controlled trial (RCT) in patients with a previous exacerbation who would not have been diagnosed with screening. In patients with very severe COPD and resting hypoxia, oxygen therapy is associated with lower mortality. Pulmonary rehabilitation is associated with markers of better health status in selected patients.
  
  Because most therapeutic trials did not include patients with mild or moderate COPD, and none included patients with airflow obstruction who did not recognize or report symptoms, it is difficult to draw conclusions regarding the potential benefits of early diagnosis through screening.
  
  
• What are the adverse effects associated with treatments of COPD?
  
  Inhaled COPD treatments are frequently associated with minor adverse effects. Evidence is mixed and inconclusive regarding major adverse effects, such as fractures, cardiovascular events, and mortality.
  
  
• Is vaccination against influenza and pneumococcus associated with decreased morbidity and mortality from COPD?
  
  Although influenza vaccination is associated with decreased exacerbations in patients with COPD, evidence is insufficient regarding benefits of pneumococcal vaccination. It is unclear whether the benefits of immunization vary based on severity of COPD, and these data do not support making vaccination a top priority based on spirometric measurements. Both vaccines seem to be well tolerated.
  
  
• What are the adverse effects of influenza and pneumococcal immunizations in patients with COPD?
  
  Both vaccines seem to be well tolerated.
  
  

"In conclusion, screening for COPD using spirometry is likely to identify a predominance of patients with mild to moderate airflow obstruction who would not experience additional health benefits if labeled as having COPD," the reviewers conclude. "A few individuals with severe airflow obstruction (FEV₁ [forced expiratory volume in 1 second] < 50% of predicted) might benefit from pharmacologic treatments that reduce exacerbations. Hundreds of patients would need to have screening spirometry to identify 1 person with COPD whose incremental health benefit over clinical diagnosis would probably be limited to the avoidance of a first exacerbation."

The AHRQ supports the work of the USPSTF, and this review did not receive separate funding. The review authors have disclosed no relevant financial relationships.

Ann Intern Med. Published online March 3, 2008.

Clinical Context

Study Highlights

• The authors conducted supplemental searches of the literature for screening programs that included evidence of efficacy and harm and use of spirometry as a motivational tool for smoking cessation.
• Included were all studies of spirometry in laboratories and offices.
• Randomized clinical trials, systematic reviews, and meta-analyses were included for studies of screening and treatment.
• For evidence of harms, nonrandomized trials generalizable to primary care populations were included.
• No published studies examined whether screening for COPD with spirometry reduced morbidity and mortality.
• The prevalence of COPD was estimated from 7 countries at 4.5% to 21.1% depending on the definition used (American Thoracic Society vs GOLD criteria).
• Severe airflow obstruction was more prevalent among older adults and current or past smokers.
• In adults aged 50 to 59 years, prevalence was 2.6% and increased to 4.2% in those aged 70 to 74 years.
• Among current smokers, 2.1% had severe obstruction vs 1% of never-smokers.
• 21% of those with an FEV₁ less than 50% predicted had no symptoms, and respiratory symptoms did not correlate with the presence or degree of obstruction.
• 90% of patients with undetected airflow obstruction had an FEV₁ of 50% of predicted or greater, and the efficacy of COPD treatments has been established only in symptomatic patients with an FEV₁ less than 50% of predicted.
• No evidence suggests that spirometry causes any significant adverse effects.
• Of 8 RCTs and 2 systematic reviews, only 2 RCTs examined the effect of spirometry on smoking cessation and no significant effect was found, but more studies are needed because studies did not control for other interventions.
• Supplemental oxygen reduced mortality in patients with resting hypoxia with an odds ratio of 0.61.
• Inhaled therapies reduced COPD exacerbations in those with COPD, with a relative risk reduction of 13% to 17% and an absolute risk reduction of 4% to 6%.
• Long-acting anticholinergics reduced the proportion of patients who required hospitalization vs placebo in 1 study (absolute risk reduction, 2%).
• In those with severe COPD, particularly in subgroups of women and former smokers, inhaled corticosteroids reduced all-cause mortality after 1 year by 1% vs placebo in pooled studies.
• None of the therapies have been tested in asymptomatic patients with airflow obstruction detected by spirometry.
• Adverse effects of treatment included bruising, tachycardia, reduced bone density, oral candidiasis, and dry mouth.
• 2 Cochrane systematic reviews showed that influenza vaccination reduced COPD exacerbations occurring more than 4 weeks after vaccination but that pneumococcal vaccination had no significant effect on health outcomes.
• Because most patients with COPD qualify for influenza vaccination according to age, the data do not support making vaccination a top priority based on spirometry findings.
• The authors concluded that spirometry as a screening tool was likely to identify a predominance of patients with mild to moderate airflow obstruction who would not experience additional health benefits if labeled as having COPD.
• Hundreds of patients would need to have screening spirometry to identify 1 person with COPD whose incremental health benefit vs a clinical diagnosis would be limited to avoidance of a first exacerbation.
• Thus, the USPSTF did not recommend routine screening for COPD with spirometry.

Pearls for Practice

• The prevalence of COPD is higher in older adults and in former and current smokers, and the USPSTF does not recommend spirometry as a routine screening tool.
• Spirometry is likely to identify a predominance of patients with mild to moderate airflow obstruction COPD who would not receive any additional health benefit if described as having COPD. Many patients would need screening to identity 1 person with COPD to avoid a single exacerbation.

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