Prevalence, stability, and clinical significance of an isolated low FEV₁ spirometry pattern in children

Objectives In adults, an isolated low FEV 1 pattern (an FEV 1 below the lower limit of normal with a preserved FVC and FEV 1 /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 1 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 1 pattern, we evaluated spirometry technique. We also examined the association of having a test with an isolated low FEV 1 pattern with clinical markers of disease severity in a subgroup of children with cystic fibrosis (CF). Results The isolated low FEV 1 pattern was uncommon across the 29,979 tests included ( n = 645 [2%]). In the 263 children with an isolated low FEV 1 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 1 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 1 pattern ( n = 50) was satisfactory. In the subgroup of children with CF ( n = 102), those who had a test with an isolated low FEV 1 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 1 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.