Background: KL-6 is a human glycoprotein secreted by type II alveolar cells in lung, and its serum levels increase in pneumonia of various causes. KL-6 is a member of the MUC-1 family, which is expressed in lung, cornea, and conjunctiva. The purpose of the present study was to investigate the clinical usefulness of quantifying serum KL-6 levels for diagnosing sarcoidosis in patients with uveitis.
Methods: Sera were obtained from 24 uveitis patients diagnosed with sarcoidosis, 37 uveitis patients with other etiologies, and 138 healthy control subjects. Serum concentration of KL-6 was determined by a human KL-6 electrochemiluminescence immunoassay.
Results: The average level of KL-6 in the sera of uveitis patients with sarcoidosis was 387 U/ml. This was significantly higher than in healthy subjects and uveitis patients with other etiologies. The KL-6 measurements identified 45.8% of sarcoidosis-positive patients. When the KL-6 results were combined with serum angiotensin-converting enzyme (ACE) concentrations, 87.5% of sarcoidosis patients were identified, compared to 66.7% using ACE results alone. The combined measurement identified 10.8% of the non-sarcoid patients and 0.72% of healthy subjects as positive (false positive).
Conclusion: Combined measurements of serum KL-6 and ACE may be useful as a screening for sarcoidosis in uveitis patients.