Spirometry Rarely Used for COPD Diagnosis

ANN ARBOR, Mich., Aug. 14 -- Only one in three patients who are told they have chronic obstructive pulmonary disease (COPD) have had that diagnosis confirmed with spirometry.

That finding emerged from a retrospective review of health records of more than 5,000 COPD patients published in the August issue of CHEST.

Earlier studies have suggested that women were less likely to undergo spirometry, but this analysis found that use of the technique was more common for women than men (33.5% versus 29.4%, P=0.001), wrote MeiLan K. Han, M.D., M.S., of the University of Michigan here, and colleagues.

Dr. Han said that without spirometry "both under diagnosis and misdiagnosis may occur, which can lead to improper therapies being prescribed."

The researchers analyzed data from five health plans recruited by the National Committee for Quality Assurance to determine the proportion of newly diagnosed COPD patients who had received spirometry during the interval beginning 720 days before COPD diagnosis and ending 180 days after diagnosis.

Patients age 40 or older who were diagnosed from July 1, 2002 through June 30, 2003 were included in the study. A total of 5,039 eligible patients were identified.

Among the findings:

• Patients ages 40 to 64 had the highest percentage of new COPD diagnoses.
• Spirometry was least likely to be used when diagnosing patients 75 or older.
• Approximately 60% of spirometry was done in the outpatient setting, as recommended by the National Lung Health Education Program.
• Only 15% of newly diagnosed COPD patients 85 or older underwent spirometry testing.

The findings of this study "are in contrast to those obtained by investigators who have queried physicians regarding their use of spirometry to confirm COPD diagnosis, in which at least 70% of physicians reported using spirometry for establishing a diagnosis," wrote Dr. Han.

"This suggests there may be a difference between what physicians report and how they actually practice," continued Dr. Han.

In an editorial that accompanied the study, Paul Enright, M.D., of the University of Arizona, Tucson, and Philip Quanjer, M.D., of Erasmus University Medical Center in Rotterdam, caution against over-reacting to the findings.

Drs. Enright and Quanjer wrote that either a widespread promotion of spirometry for COPD screening -- as "generously funded by pharmaceutical companies in some countries" -- or continued promotion of office spirometry testing for every adult smoker have the potential for causing more harm than good.

A better response, they said, would be to use spirometry to detect COPD in current or former smokers who have "high pretest probability of COPD." That probability would be determined by clinical assessment and use of a structured questionnaire.

For example, an obese patient has a lower risk of COPD than does a patient with a history of allergies. More pack years of smoking and dyspnea on exertion also make COPD more likely, they noted.

Importantly, Drs. Enright and Quanjer wrote that unless FEV₁ is < 50% of predicted "from a good quality baseline spirometry test, the diagnosis of COPD should not be made without performing spirometry after an inhaled bronchodilator (post-BD), as recommended by the Global Initiative for Chronic Obstructive Lung Disease guidelines."

The National Lung Health Education Program recommends spirometry testing for current and former smokers ages 45 and older, as well as any patient who experiences cough, shortness of breath with exertion, or wheezing.