The ATS has developed criteria suggesting that a significant post-bronchodilator FEV1 response is 200 ml and 12% improvement. To our knowledge, the ATS criteria never been validated versus the clinical diagnosis of asthma.
All spirometry tests done from Sept 1999 to Sept 2004 were analyzed for meeting the ATS criteria for FEV1 improvement There were a total of 1862 tests meeting the ATS FEV1 criteria with a total of 644 individual non-duplicate records. A total of 311 individual patient records were analyzed for staff respirologists.
311 patients were found who met ATS FEV1 criteria and whose complete physician records were available. There were 170 men and 141 women with a median age of 62.8 years. Of the 311 patients meeting a 12% FEV1 change, there were 170 (54.7%) diagnosed by the staff respirologist with asthma. Of the 208 patients meeting a 15% FEV1 improvement, there were 120 (57.7%) diagnosed with asthma. Of the 98 patients meeting a 20% FEV1 improvement, there were 62 (63.3%) patients diagnosed by the staff respirologist with asthma. For the diagnosis of asthma versus not asthma, there was a statistically significant difference in the post-bronchodilator FEV1 % improvement with p=0.02 (CI 0.256-3.02). Of the 170 patients with asthma (for 12% FEV1 response), there was a mean improvement in FEV1 of 19.4% (SD 6.87), while the 140 not asthma patients had a mean improvement in FEV1 of 17.8% (SD 5.53).
While the ATS FEV1 criteria are a help in asthma diagnosis, relying on spirometric criteria alone is inadequate in asthma diagnosis. Only 170 patients (54.7%) meeting ATS bronchodilator improvement criteria were felt to clinically have asthma.
The diagnosis of asthma requires a clinical history and physical examination. Spirometry changes are helpful but the level of bronchodilator significance remains unclear.
John Gjevre, None.