Exhaled breath condensate cytokine level as a diagnostic tool for obstructive sleep apnea syndrome.

BACKGROUND Relationships between exhaled breath condensate (EBC) and serum cytokines and apnea-hypopnea index (AHI) in patients with excessive daytime sleepiness and loud snoring were evaluated for their potential to predict the severity of obstructive sleep apnea syndrome (OSAS). METHODS Non-smoking patients with suspected OSAS who had undergone polysomnography (PSG) were selected until 22 non-OSAS, and 22 mild, 22 moderate and 24 severe OSAS cases based on AHI were achieved. Ten healthy smokers served as a smoker control group. Interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha), and 8-isoprostane were measured in EBC and serum on the morning after PSG and related to OSAS severity using linear discriminant analysis (LDA) and logistic regression (LR). RESULTS Biomarker levels, in both EBC and serum, differed significantly across the four groups. Classification by LDA using IL-10 in EBC showed the highest agreement with AHI classification (kappa=0.88). LR distinguished moderate and severe OSAS from mild OSAS and non-OSAS perfectly using IL-6 in EBC and almost perfectly using IL-10 in EBC (area under the ROC curve=0.997). The levels of biomarkers among smokers overlapped with mild to severe OSAS patients. CONCLUSIONS Among non-smoker OSAS suspects, EBC IL-6 and IL-10 have potential to predict severity of OSAS.