Background Calprotectin is a highly immunogenic molecule principally expressed in the cytosol of granulocytes and monocytes. Serum calprotectin levels are increased in different inflammatory conditions such as bacterial infections, inflammatory joint diseases and cystic fibrosis.

It has been suggested that measurement of serum calprotectin levels may be a sensitive indicator of disease activity in patients with endogenous posterior uveitis and that this molecule could play a role in the clearance of inflammatory cells at the late phase of uveitis.

Objectives Main objective:To determine serum calprotectin levels in patients with active non infectious endogenous uveitis.

Secondary objectives: To compare serum calprotectin levels with those of a control cohort of healthy volunteers.

Methods Study type: transversal study.

Patients: Uveitis cohort: patients with active non infectious endogenous uveitis. Control cohort: healthy volunteers.

Stadistic analysis: Proportions for categorical variables and average ± SD (or median if appropiate) for continuous variables were calculated. Categorical variables were compared by chi-square test (applying continuity correction if necessary). T-test (or Kruskal-Wallis if appropiate) was used to compare averages. Spearman coefficient was calculated in order to stablish correlation between continous and ordinal variables.

Results 22 uveitis patients and 8 healthy volunteers were included.

From 22 patients with uveitis, 14 were diagnosed with anterior uveitis, 1 with intermediate uveitis, 5 with posterior uveitis and 2 with panuveitis. 17 patients had received corticosteriods (topical, systemic or periocular) previously to the serological determination. 9 were diagnosed with another inflammatory disease: spondyloarthritis (4), Crohn's disease (2), pulmonary sarcoidosis (1), psoriasis (1), systemic sclerosis (1).

No statistically significant differences were observed between both cohorts regarding age (p=0.156) and gender (p=0.554).

The median of calprotectin levels was higher in the uveitis cohort than in the control cohort (637.5 vs 396 mg/kg), although the difference didn't reached statistically significance (p=0.174).

No statistically significant differences were found between patients who were diagnosed with another inflammatory disease and those who weren't (p=0.548).

Taking into account anterior uveitis, a moderate-good correlation was observed between Tyndall degree and serum calprotectin levels (Spearman ρ=0.627, p=0.016).

Conclusions In our study, serum calprotectin levels were higher in patients with active non infectious endogenous uveitis than in healthy volunteers, although this difference didn't reach statistical significance. A moderate-good correlation was observed between Tyndall degree and serum calprotectin levels.

This work is limited by the small sample size. Results are probably influenced by previous use of corticosteroids in the most part of patients.

Disclosure of Interest None declared