Diagnosis

The diagnosis of COPD is based on clinical criteria. The clinician arrives at a diagnosis only after careful consideration of the patient's history and physical examination, radiographic studies, pulmonary function studies, and certain laboratory tests. There is a recent justifiable emphasis on diagnosing COPD in its early, often asymptomatic stages by demonstrating abnormal fev1 values. Early intervention, especially smoking cessation, will improve pulmonary function or at least greatly slow the progress of airways obstruction. This disease should not be allowed to progress to its final stages before it is recognized and treated.

The primary care physician is in an ideal position to recognize COPD at its earliest stages, even before symptoms are present. Smokers should be screened systematically for airflow reduction by spirometry in the physician's office, just as other patients are screened for illnesses such as hypertension, hyperlipidemia, breast cancer, and uterine cancer.

Spirometry is the key test, but a questionnaire can also be helpful in screening for COPD and should be part of every patient's chart. Important items of information include:

1. Family History: Note history of allergies, emphysema, cystic fibrosis, COPD, and other chronic lung conditions.
2. Smoking History: Indicate age of smoking initiation and number of packs smoked per day.
3. Detailed Occupational History: Detail any exposure to noxious inhalants.
4. History of Respiratory Tract Infections: Note frequency and severity.
5. Current Symptoms: Document dyspnea, cough, wheezing, sputum production, and chest pain.

There are many standardized forms available to the physician for documenting the pulmonary history. A sample form is found in Appendix A.

The most common presenting complaint in a patient with COPD is dyspnea on exertion, a symptom that develops late in the course of this disease. The patient may not acknowledge the classic early symptoms: morning cough and sputum production. A history of recurrent respiratory tract infections, which are usually prolonged and often require antibiotic treatment, is common. A childhood history of frequent respiratory tract infections and bronchitis may indicate the presence of asthma at an early age. Any history of typical asthma, recurrent sinus infections, or nasal polyps should be noted, because such conditions are common in patients with COPD. A smoking history is, obviously, of paramount importance.

Complaints of dyspnea, cough, and sputum production may be associated with a number of other pulmonary and nonpulmonary problems. The primary care physician should exclude other conditions such as neoplasm, cardiac failure, infection, inflammatory disease, and genetic and hypersensitivity diseases. These, of course, may coexist with COPD.

The patient's physical examination is likely to be entirely normal early in the course of COPD. However, decreased breath sounds, wheezes, and crackles at the bases might be observed, especially during exacerbations. Pursed-lip breathing, intercostal retractions, edema, cyanosis, and evidence of weight loss are seen only with advanced disease.

Radiographic Studies

Both posteroanterior and lateral chest x-rays are required in the evaluation of COPD, but they are of no value as screening tools. Chest x-rays are useful in ruling out other causes of respiratory symptoms. The finding of apparently hyperlucent lungs has frequently led to the false diagnosis of airways obstruction. X-rays can show low, flat diaphragms, enlarged retrosternal air space, sparse vasculature in the periphery of the lung fields, bullous lesions, and pul-monary artery prominence, but these develop only in the later stages of COPD.

Computerized tomography, (CT), scans are rarely indicated, but the use of high-resolution, thin-cut ct images is currently being evaluated in the diagnosis of interstitial lung disease. The technique may prove to be of value in assessing the early stages of COPD in selected patients. CT is also helpful in the early diagnosis of COPD, where the risk of lung cancer is high.

Electrocardiogram

The electrocardiogram is normal in the early stages of COPD, but peaked P-waves in II, III, AVF, decreased voltage of QRS, and right axis deviation are often noted in advanced stages of disease. Supraventricular arrhythmias are commonly found as well, especially during exacerbations.

Laboratory Screening

Testing in the clinical laboratory is rarely useful in the diagnosis of COPD. Patients with a family history of severe, early-onset emphysema, however, should be screened for alpha-1-antitrypsin deficiency. Also, secondary erythrocytosis may reflect chronic hypoxemia, a late manifestation.

Spirometry

A spirometer used for screening purposes must be available to the primary care physician in the office setting. Spirometry is used to identify patients with COPD by measuring their expiratory flow rates and vital capacity. It may be used to assess the severity of a patient's disease. Serial tests allow the physician to measure the patient’s response to therapy. The use of spirometry has also been shown to be a useful tool in motivating patients to stop smoking.

There is little to support routine screening in the general population. But smokers and other patients exposed to injurious inhalants should be routinely screened. All patients who complain of dyspnea or unexplained cough should receive pulmonary function tests.

The forced vital capacity (FVC), the forced expiratory volume in one second (FEV1), and the ratio of these two (FEV1/FVC), are the primary spirometric measurements used for diagnosis. A reduced FEV1/FVC (less than 70%), indicates airways obstruction. The severity of airflow obstruction is also reflected in the FEV1. A reduced FVC may suggest restrictive dysfunction, but this cannot be determined reliably by spirometry alone.

As discussed in Section M, the National Lung Health Education Program, (NLHEP), the FEV6 is used as a surrogate marker for FVC. The advantage is more convenience in clinical spirometric testing. The FEV1/FEV6 ratio tracks the classic FEV1/FVC ratio quite accurately, and identifies patients at risk of rapid declines in FEV1 over time.

Repeating spirometric tests after administering an inhaled bronchodilator to patients may help identify a bronchospastic element of their disease. An improvement in the FVC or FEV1 of 15% or more, according to American Thoracic Society standards, indicates a positive response. Failure to respond does not necessarily mean that a patient will not find bronchodilators or corticosteroids helpful. Many manufacturers sell spirometers that give rapid results. Many are computerized and their use requires little training. All equipment should meet the American Thoracic Society’s performance recommendations and should be calibrated regularly to assure continued accuracy. It is strongly recommended that physicians use a spirometer that produces a hard copy of the flow-volume loop and/or the time-volume curve for inclusion in the patient’s chart.

Complete pulmonary function studies are not necessary in the routine evaluation of early COPD. Indications for referral to the pulmonary function laboratory include:

1. The evaluation of dyspnea of uncertain etiology.
2. Disability evaluation.
3. Preoperative evaluation of a patient requiring thoracic or intra-abdominal surgery.

Specific tests can help in the diagnosis and treatment of conditions related to COPD. Hyperinflation is manifested in COPD by an increase in total lung capacity and an increase in the ratio of residual volume to total lung volume capacity. Emphysema or interstitial lung disease is suggested by a reduction in the diffusing capacity. The use of pulse oximetry to estimate oxygen saturation is useful, but arterial blood gas measurements are necessary to assess and manage patients during exacerbations and when oxygen therapy is prescribed.

References

American Thoracic Society. Lung function testing, selection of reference values, and interpretation strategies. Am Rev Resp Dis 1991;144:1202-1218. An excellent source of useful information.

American Thoracic Society. Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease (COPD) and asthma. An official statement of the American Thoracic Society. Am Rev Respir Dis 1987;136:225-245. This is a well-referenced six-chapter review on useful approaches to the diagnosis of COPD and associated asthma.

Crapo RO. Current concepts: Pulmonary function testing. N Engl J Med 1994;331:25-30. All the primary care physician needs to know about pulmonary function testing.

Ferguson GT, Enright PL, Buist AS, Higgins MW. Office spirometry for lung health assessment in adults. A consensus statement from the National Lung Health Education Program, (nlhep). Chest 2000;117:1146-1161. This consensus statement from the nlhep recommends spirometric testing for all smokers over age 45 and anyone with dyspnea, cough, mucus, or wheeze.

Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from a sample of the general U.S. population. Am J Respir Crit Care Med 1999;159:179-187. An update review of spirometric reference values from a large randomized sample of the United States population. The fev6 is a good surrogate marker of fvc and the fev1/fev6 ratio is useful in identifying subjects with rapid rates of decline in fev.