Elevation of surfactant protein D, a pulmonary disease biomarker, in the sera of uveitis patients with sarcoidosis.

PURPOSE: Surfactant protein D (SP-D) is found in the epithelial cells of multiple mucosal surfaces. It is commonly used to diagnose and screen for pulmonary diseases. In the present study, serum levels of SP-D were measured in patients with uveitis to ascertain whether SP-D is a clinically useful laboratory parameter to diagnose sarcoidosis.

METHODS

Sera were obtained from 81 patients with sarcoidosis, 16 patients with Behçet disease, 40 patients with HLA-B27 associated uveitis, 50 patients with Vogt-Koyanagi-Harada (VKH) disease, and 33 healthy volunteers. Serum SP-D levels were quantified with an SP-D enzyme immunoassay kit.

RESULTS

In the healthy control subjects, the average serum SP-D level was 39.70 ng/ml; in the uveitis patients with sarcoidosis, the mean serum SP-D level was 57.0 ng/ml, and in the uveitis patients with other etiologies the mean levels were 38.63 ng/ml for Behçet disease, 38.18 ng/ml for HLA-B27 associated uveitis, and 31.32 ng/ml for the VKH patients. The average serum SP-D levels of patients with sarcoidosis were significantly higher than those of patients with any other uveitis etiologies or healthy controls (P < 0.01).

CONCLUSIONS

SP-D may be a less invasive and less expensive laboratory examination for sarcoidosis screening. SP-D should be considered as a new laboratory parameter for the diagnosis of uveitis and sarcoidosis.