Prevalence, stability, and clinical significance of an isolated low FEV spirometry pattern in children.

Objectives: In adults, an isolated low FEV pattern (an FEV below the lower limit of normal with a preserved FVC and FEV/FVC) has been associated with the risk of developing airway obstruction. Our objective was to examine the prevalence, stability, and clinical significance of an isolated low FEV pattern in the pediatric population.

Methods: We conducted a retrospective study of spirometries from children ages 6-21 years and categorized tests into spirometry patterns according to published guidelines and recent literature. In a subgroup of tests with an isolated low FEV pattern, we evaluated spirometry technique. We also examined the association of having a test with an isolated low FEV pattern with clinical markers of disease severity in a subgroup of children with cystic fibrosis (CF).

Results: The isolated low FEV pattern was uncommon across the 29,979 tests included (n = 645 [2%]). In the 263 children with an isolated low FEV pattern who had a follow-up test performed, the most frequent spirometry pattern at last test was normal (n = 123 [47%]). A primary diagnosis of CF was associated with increased odds of having at least one test with an isolated low FEV pattern (OR = 8.37, 95% CI = 4.70-15.96, p < .001). The spirometry quality in a subgroup of tests with an isolated low FEV pattern (n = 50) was satisfactory. In the subgroup of children with CF (n = 102), those who had a test with an isolated low FEV pattern had higher odds of using oral antibiotics in the last 12 months than those who had a normal pattern (OR = 3.50, 95% CI = 1.15-10.63, p = .03).

Conclusions: The isolated low FEV pattern can occur repeatedly over time, usually transitions to a normal pattern, is not due to a poor spirometry technique, and could be clinically relevant in children with chronic lung diseases.