New biomarker reflects intraocular inflammation in uveitis patients

In this study, the authors investigate the association between circulating S100A8/A9 levels and uveitis activity. S100A8 and S100A9 (also known as MRP8 and MRP14) are Ca²⁺binding proteins that belong to the S100 family and help facilitate recruitment of leukocytes, promotion of cytokine and chemokine secretion, and regulation of leukocyte adhesion and migration. 

Study design

This single-center study included plasma samples from 549 patients (454 cases, 95 controls) to determine if circulating S100A8/A9 levels correlate with ophthalmic inflammatory activity. The cohort had their uveitis defined and anatomically classified using the SUN criteria and active inflammation was defined as greater than 0.5+ anterior chamber cell.

Outcomes

Every active uveitis group showed elevated levels of S100A8/A9 compared with the control group. After corticosteroid treatment, serum S100A8/A9 levels decreased in parallel with inflammation severity.

Patients with acute anterior uveitis (AAU) and ankylosing spondylitis (AS) had higher levels of S100A8/A9 compared with those patients who had AAU alone without AS.

Limitations

This was a single-center study conducted in China. Patients were grouped only by activity or no activity, and not sub-grouped by amount of activity. This activity was also only determined by anterior inflammation. Sensitivity, specificity and positive predictive value of this marker were not provided by the authors.

Clinical significance

This study suggests S100A8/A9 could be used as a systemic marker to track uveitis activity, though is limited as it only is related to anterior inflammation which can be viewed on exam. The biomarker may be helpful in determining which patients with AAU will go on to develop AS if they have no symptoms on review or systems. It may also serve as a potential target for future medications that could prevent inflammatory activity.