RATIONALE: Treatment guidelines highlight the role of pulmonary function tests (PFT) in asthma diagnosis confirmation and follow-up assessments of future risk. Clinical studies have reported that lung function is not strongly correlated with asthma symptoms; however, real-world data on the association of lung function and symptom control is currently limited. This study assessed the level of control and explored the relationship to lung function and prior exacerbations in asthma patients seen by U.S. specialists.
METHODS: A multi-site, cross-sectional study was conducted from January 21 to April 29, 2019 in adult asthma patients recruited from 24 pulmonary and allergy clinics. Eligible subjects presented to the specialists’ office for a routine or symptomatic visit, had a physician diagnosis of asthma, used an ICS-containing maintenance medication ≥1 time within past 4 weeks; with no history of COPD, chronic bronchitis or emphysema. Patients completed an electronic questionnaire that included the Asthma Control Test (ACT), demographics, medical history, and asthma treatment. Asthma control was defined as “Well Controlled” (ACT score ≥20) and “Not Well Controlled” (ACT ≤19). Sites abstracted available spirometry data from patient charts.
RESULTS: 774 patients met eligibility criteria; mean (SD) age was 54.5 (16.2) years, 74.2% female, 259 patients had pre-bronchodilator PFT measurements available on the same day the questionnaire was completed. 52% (n=134/259) of the group were not well controlled per the ACT. Well controlled patients were largely undifferentiated compared with those not well controlled on mean FEV1 (2.4L vs 2.2L) and mean % predicted FEV1 (80.9% vs 77.0%). Among patients reporting a symptomatic reason for visit and same-day % predicted FEV1 measurement (n=61), normal lung function (aka mild: FEV1>80%) was observed in 43% (n=26) and abnormal lung function in 57% (n=35) of patients; 38% (n=23/61) were moderate (FEV1=60-80%) and 20% (n=12/61) severe (FEV1<60%). There were no differences in the percentage of patients with same-day PFT measurements, reporting 1 exacerbation in the previous year among those well controlled vs not well controlled. Yet, ≥2 asthma exacerbations were reported more frequently among not well controlled patients (47.0%) than in well controlled (19.2%).
CONCLUSION: The findings provide real-world insights supporting the uncoupling of PFTs and symptom control and a potential association between asthma control and frequent exacerbations in asthma patients receiving care at specialty clinics in the U.S., highlighting the importance of using patient-reported measures such as the ACT to assess control/symptoms rather than relying solely on lung function.
