美国预防服务工作组（USPSTF）近期发表建议，总结了采用肺呼吸量测定法筛查慢性阻塞性肺病（COPD）的证据。最新的指南发表在美国《内科学纪事》（Annals of Internal Medicine）“新闻早知道”栏目里。

　　美国国家健康保健研究与质量机构（AHRQ）的Kenneth Lin医生与USPSTF的同事们写到：“在美国2400万气流阻塞患者中，只有不到一半的患者进行了COPD诊断，而且诊断通常出现在疾病的中晚期。因为五分之四的COPD患者为烟民或有过抽烟史，有些团体就主张采用肺呼吸量测定法对无症状的抽烟者进行大规模筛查。从理论上来说，早期发现能够通过以下方式改善患者的健康状况：提高戒烟率；注射流感疫苗和肺炎球菌疫苗；较早开始药物治疗、氧气疗法或肺疾病康复疗法等。”

　　USPSTF审查了通过以下方式检索到的英文文章：检索2007年1月的PubMed和Cochrane图书馆、近期的系统综述、专家意见以及文章的参考文献。同时还提及了使用肺呼吸量测定法筛查COPD益处和害处的八个主要问题；对合适的研究类型所涉及的具体准入标准和淘汰标准也有所探讨。我们采用预定的USPSTF标准来概括和界定研究的质量。
尽管药物疗法对治疗COPD会减少重症患者的急性发作，但是严重的COPD在美国却并不多见。目前仍没有证据证明单独采用肺呼吸量测定法能够提高戒烟率。筛查会带来潜在的伤害，比如说如果结果呈假阳性，那么不必要的治疗将会产生一定的不良反应。
　　利用全美气流阻塞患者的数据，USPSTF在筛查人群年龄和抽烟状态的基础上预测了结果。在通过审查的研究中，没有一项研究能够提供与COPD筛查健康结果有关的直接证据。
审查作者写到：“使用肺呼吸量测定法筛查COPD可能会帮助轻中度的气流阻塞患者确定更好的治疗方案，这些患者如果被确诊为COPD，那么将不能享受保健福利金。数百名患者需要通过呼吸量测定法来延迟病情的恶化。”
关于使用肺呼吸量测定法进行COPD筛查的益处和害处的主要问题，以及回答这些问题的证据总结如下：
　 ·使用肺呼吸量测定法筛查COPD能够降低发病率和死亡率吗？
　　已经发表的对照研究中没有对这个问题的回答。
　 ·什么是流行性COPD，风险因素真的能把高风险人群从普通患者中区分出来吗？
　　虽然在初诊中发现不了这些症状，但是在美国人中仍有约1/14成年人的气流阻塞与COPD症状一致。 单纯的根据症状来诊断COPD会导致对非气流阻塞患者的过度诊断。尽管年龄和抽烟史的增加与严重疾病的风险增加有关，但是这些因素对于区别高风险患者和普通风险患者来说并不可靠。
　 ·采用肺呼吸量测定法筛查COPD的副作用有哪些？
　　虽然假阳性的结果在无症状健康人身上的概率占到了基线百分比，但是迄今为止仍然没有证据表明肺呼吸量测定法与临床上任何严重的副作用有关。

　 ·与其他抽烟者相比，通过肺呼吸量测定法筛查出的COPD抽烟者具有更好的戒烟率吗？
关于肺呼吸量测定法是戒烟的独立诱发因素的说法，目前证据尚不明确。大部分研究的局限性包括：没有将肺呼吸量测定法与其他提高戒烟率的疗法独立出来进行评估、样本量太小不足以发现显著的统计学效果、干预措施的异质性、防止Meta分析的疗效。

·药物治疗、氧气疗法或COPD患者的肺康复与发病率和死亡率的增加有关系吗？
对于有临床症状、症状严重的COPD患者，药物治疗也许可以减少疾病的恶化和全因死亡率。但是，降低死亡率最有力的证据来自于一项随机对照试验（RCT），这些患者先前均没有被确诊。在严重COPD患者和缺氧患者中，氧气疗法与较低的死亡率有关系。在选定的患者中，肺部疾病的康复与患者健康状况良好有一定的关联。
由于大部分治疗试验不包括症状轻微或慢性COPD患者，也不包括无症状的气流阻塞患者，所以很难根据筛查得出的初步诊断来得出结论。
　　·哪些不良影响与治疗COPD有关？
　　吸入治疗COPD通常与轻度不良影响有关。与重大不良影响（如骨折、心血管事件、死亡率等）有关的证据目前还不确定。
　　·流感疫苗和肺炎球菌疫苗与COPD发病率和死亡率的降低有关吗？
　　尽管流感疫苗与COPD患者病情恶化率降低有关，但是还没有足够的证据来证明肺炎球菌疫苗也与此有关。目前我们还不确定免疫的益处是否随COPD的严重程度而改变，这些数据也不支持在吸气策略中首选疫苗接种。两种疫苗似乎都有很好的耐受性。
　　·流感疫苗和肺炎球菌疫苗对COPD患者有哪些不良影响？
　　两种疫苗似乎都有很好的耐受性。
AHRQ支持USPSTF的工作，而且该项审查没有接受任何独立资金赞助。

Screening for COPD With Spirometry Reviewed 
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.
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.

[责任编辑:刘聪]