High-Sensitivity C-Reactive Protein Can Reflect Small Airway Obstruction in Childhood Asthma

High-sensitivity assays enabled the identification of C-reactive protein (hs-CRP) at levels that were previously undetectable. We aimed to determine if hs-CRP could reflect airway inflammation in children, by comparing hs-CRP with spirometry and impulse oscillometry (IOS) parameters and symptomatic severities.

A total of 276 asthmatic children who visited Severance Children's Hospital from 2012-2014 were enrolled. Serum hs-CRP and pulmonary function tests were performed on the same day. Patients were divided into hs-CRP positive and negative groups (cut-off value, 3.0 mg/L).

Of the 276 asthmatic children [median age 7.5 (5.9/10.1) years, 171 boys (62%)], 39 were hs-CRP positive and 237 were negative. Regarding spirometry parameters, we observed significant differences in maximum mid-expiratory flow, % predicted (FEF₂₅₋₇₅) (p=0.010) between hs-CRP positive and negative groups, and a negative correlation between FEF₂₅₋₇₅ and hs-CRP. There were significant differences in the reactance area (AX) (p=0.046), difference between resistance at 5 Hz and 20 Hz (R5-R20) (p=0.027), resistance at 5 Hz, % predicted (R5) (p=0.027), and reactance at 5 Hz, % predicted (X5) (p=0.041) between hs-CRP positive and negative groups. There were significant positive correlations between hs-CRP and R5 (r=0.163, p=0.008), and X5 (r=0.164, p=0.007). Spirometry and IOS parameters had more relevance in patients with higher blood neutrophil levels in comparison to hs-CRP.

Hs-CRP showed significant correlation with FEF₂₅₋₇₅, R5, and X5. It can reflect small airway obstruction in childhood asthma, and it is more prominent in neutrophil dominant inflammation.