S100B in serum and saliva: a valid invasive or non-invasive biomarker in obstructive sleep apnea?

M. Traxdorf, O. Wendler, K. Tziridis, J. Bauer, C. Scherl

Department of Otorhinolaryngology, Head & Neck Surgery, Friedrich-Alexander University Erlangen-Nürnberg (FAU), Erlangen, Germany. maximilian.traxdorf@uk-erlangen.de

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• Respiratory Medicine

OBJECTIVE:  The aim of this prospective study was to determine whether serum or saliva S100B could be established as an invasive or non-invasive biomarker of cerebrovascular stress due to chronic intermittent hypoxia in obstructive sleep apnea (OSA).

PATIENTS AND METHODS: S100B levels in serum and saliva were measured by an enzyme-linked immunosorbent assay (ELISA) in 40 patients with polysomnographically confirmed OSA (n=34) or ronchopathy (n=6) and 20 control subjects (n=20). We also investigated four healthy volunteers (n=4) to determine whether the S100B levels in serum and saliva are dependent on the time of day.

RESULTS: Serum S100B was significantly higher in OSA than in healthy control subjects (p=0.007), although it was not related to the severity of OSA and was independent of age, sex, and subjective daytime symptoms. Values of S100B in saliva showed a marked scatter, so there was no significant difference between the OSA group and controls (p=0.62). We did not find that S100B levels in either serum or saliva depended on the time of day (p=0.53; p=0.91).

CONCLUSIONS: Serum S100B allows us to discriminate healthy subjects from patients with OSA. However, it does not live up to its promise as a valid invasive predictor of OSA, since it does not correlate with the severity of the disease. Also, S100B in saliva is not suitable for use as a non-invasive biomarker to detect hypoxia-induced cerebrovascular stress in OSA. This finding prevents an S100B saliva-based assessment of risk or possible extent of structural brain damage, ruling out the possibility of non-invasive home monitoring of compliance and therapeutic efficacy in cases of OSA on treatment.

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