In our study, those with chronic dyspnea on exertion and chronic cough were more likely to have a spirometry performed, whereas current or past smoking was not associated with the use of spirometry. We found that the rate of spirometry use in those with new and existing diagnosis of COPD was quite high but not optimal. Moreover, clinician diagnosis of COPD compared to spirometry was accurate only about half of the time.
Our study is reflective of an urban medical center with a large proportion of minority patients and high rates of obesity, a population not previously represented in studies evaluating COPD and spirometry use. We found that neither of these characteristics was associated with the use or nonuse of spirometry compared to Caucasians and normal weight individuals, respectively. Previous studies using HEDIS criteria which is 2 years prior to and up to 6 months after the new clinician diagnosis of COPD show that only about a third of those with a new diagnosis of COPD had spirometry. Our study shows that primary care physicians are performing spirometry outside of the HEDIS time frame resulting in more than three-quarters of those with COPD having spirometry performed at some time during their usual care. Although this is an improvement, it shows that nearly a quarter of patients with COPD still have not had spirometry to confirm the diagnosis. This remains important as primary care physicians are only accurate in their clinical diagnosis of COPD about half the time compared to spirometry results. As spirometry testing was available in the outpatient primary care clinic, the rate of spirometry use seen in this study may be inflated compared to other clinics without spirometry in the outpatient setting.
Consistent with ATS/ERS and GOLD guidelines1,2
, primary care physicians were more likely to obtain spirometry when there was the presence of chronic dyspnea on exertion or chronic cough. However, they were less likely to obtain spirometry in the presence of chronic sputum and the results were equivocal with chronic shortness of breath. The reason for this is unclear. It is possible that sputum when considered separately may not be considered a respiratory symptom in the same category as dyspnea on exertion and cough with respect to COPD, even though listed as a key indicator for considering a diagnosis of COPD by the above guidelines. Shortness of breath alone without an indicator of any level of exertion may be too nonspecific to warrant a diagnostic test such as spirometry or not pursued in detail as the level of exertion is a way to quantitatively assess any level of shortness of breath. The lack of association of current or past smoking status and spirometry is also not consistent with ATS/ERS and GOLD guidelines, but is consistent with the U.S. Preventative Services Task Force (USPSTF) recommendation against screening for COPD.32
However, physician practice in our study, although reflective of USPSTF recommendations, could not have been in response to the guidelines as they were published in 2008 and our cohort was not followed beyond the year 2007.
Prior to this study, we assumed that the longer a patient was followed in the primary care clinic, the more likely they were to have a spirometry performed. However, that was not the case. Patients who were followed longer were less likely to get spirometry when compared to those who were followed for only up to 2 years. A possible explanation could be the competing demands in a busy practice where COPD may be less of a priority than other acute and chronic medical concerns such as hypertension and diabetes mellitus. As primary care encounters have time constraints, multiple medical conditions, patient concerns, and point of care for other chronic conditions compete for priority during a single visit. Although competing demands have not been studied for COPD, it has been shown to have a negative impact on tobacco cessation counseling.33
Once a patient has been seen, primary care physicians may be less likely to obtain spirometry unless there is a new issue (e.g. new or worsening symptoms). If these patients are being treated with respiratory medications, a new clinical paradigm may be needed to confirm diagnosis in those with pre-existing clinical diagnosis of COPD.
In our study, almost a quarter of patients without a diagnosis of COPD prior to spirometry had airways obstruction and subsequent follow-up did show a new diagnosis of COPD in about a third of these patients. We did not have appropriate follow-up time to observe all physician decision making in regards to the diagnosis of COPD post-spirometry. In future, it would be important to note if spirometry results alter the pre-test diagnosis in clinical practice or if providers are still diagnosing patients based on symptoms, history, and/or response to therapy post-spirometry.
Our study has some limitations. First, this was a single center study which limits its generalizability. However, our cohort was from an academic medical center with outpatient spirometry testing available, so the rate of spirometry use is likely much higher than the general primary care clinic setting. Second, post-bronchodilator values were not available for all spirometry results. This may have misclassified some with reversible airways disease. Third, information garnered from the primary care encounters may not be exactly reflective of the encounter. For example, a patient may complain of a symptom that is not listed in the encounter note. Fourth, we did not delineate why the spirometry was performed. For example, it may have been performed for perioperative risk assessment. Our analysis does not infer causality; however, regardless of the indication for spirometry, once performed, obstruction can be defined based on the results.
In conclusion, the use of spirometry at any time during primary care in the diagnosis of COPD was suboptimal and the symptom indicators associated with COPD and spirometry were chronic dyspnea on exertion and chronic cough which is consistent with guidelines. For patients who had a spirometry and a diagnosis of COPD, primary care physicians were accurate in their diagnosis only half of the time. Our results suggest that recommendations for the use of spirometry should emphasize confirmation of diagnosis not only when the diagnosis is new but also when the diagnosis is pre-existing.