Patients with cystic fibrosis (CF) with greater declines in forced expiratory volume in 1 second (FEV1) and respiratory symptoms had a greater likelihood of diagnosis with pulmonary exacerbations and treatment with antibiotics, according to a new study published in Pediatric Pulmonology.

FEV1 decreases between 5% and 9% (FEV15-9%) as well as 10% or greater (FEV1≥10%) were associated with greater odds of pulmonary exacerbation diagnoses when associated with increased cough (odds ratio [OR] 1.56 and OR 1.82, respectively), increased sputum (OR 1.59 and OR 1.78, respectively), and increases in both together (OR 1.51 and 1.68, respectively). Prescription of antibiotics was also associated with FEV15-9% and FEV1≥10% when present with increased cough and/or sputum.

“We demonstrated that even small changes in FEV1 in the presence of increased cough or increased sputum are associated with the diagnosis of [pulmonary exacerbations] and the use of antibiotics,” the authors said.

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The study also found that physicians do not use FEV1 alone to make diagnoses, however, as 47 patient encounters with FEV1 declines greater than 10% did not yield a pulmonary exacerbation diagnosis. The patients tended to have fewer signs and symptoms during these visits. These patients also tended to have higher baseline FEV1 values prior to declines.

“These findings highlight the extent to which clinicians use a combination of respiratory symptoms and FEV1 decline to diagnose pulmonary exacerbations and prescribe antibiotics. Understanding this dynamic is key as the pandemic-era transition to telemedicine, in addition to the already frequent practice of prescribing antibiotics via telephone, may further increase physicians’ reliance on respiratory symptoms to diagnose pulmonary exacerbations without spirometry,” the authors said.

A total of 628 clinical encounters with 178 children with CF occurred at the Riley Hospital for Children in Indianapolis, Indiana in 2019. The patients were aged between 6 and 17 years (median, 11.5) and were predominantly White (89.9%). Those visits resulted in 199 (31.7%) pulmonary exacerbation diagnoses.


Bouzek DC, Ren CL, Thompson M, Slaven JE, Sanders DB. Evaluating FEV1 decline in diagnosis and management of pulmonary exacerbations in children with cystic fibrosis. Pediatr Pulmonol. Published online April 15, 2022. doi:10.1002/ppul.25925