Exhaled nitric oxide, pulmonary function, and disease activity in children with systemic lupus erythematosus

Aim: To determine the association among fractional exhaled nitric oxide (FENO), pulmonary function, and disease activity in children with systemic lupus erythematosus (SLE).

Methods: Children aged 7-18 years, diagnosed with SLE under the criteria of the American Rheumatism Association (revised 2012), were enrolled. All eligible participants had disease activity, FENO, and pulmonary function evaluated and re-evaluated at 6-month follow-up.

Results: Twenty-four children (95.8% female; mean age 15.2 ± 2 years; median disease duration 2.4 years) were studied. The mean FENO₁ and FENO₂ were 19.6 ± 7.2 parts per billion (ppb) and 17.4 ± 4.5 ppb, respectively. At baseline, 20.8% had abnormal pulmonary functions (all restrictive defects) and increased to 29.2% at follow-up (isolated restrictive defect 25% and restrictive with diffusion defect 4.2%). Most of their disease activities at baseline and second assessment were non-active (58.3%, 70.8%) or mild disease activities (20.8% both). There was significant correlation between FENO and disease activity (r = 0.49; P-value = 0.02). The significant negative correlation between total lung capacity (TLC) and disease activity was detected in children with active SLE (r = -0.71; P-value = 0.02).

Conclusion: Decreased TLC and high FENO were common in SLE children who had no respiratory symptoms and correlated with disease activity. FENO should be considered as an additional pulmonary function to evaluate disease activity in children with SLE.