Usefulness of Combined Measurement of Serum Soluble IL-2R and Angiotensin-Converting Enzyme in the Detection of Uveitis Associated with Japanese Sarcoidosis

Purpose: Angiotensin-converting enzyme (ACE) is conventionally used as a biomarker in the diagnosis of uveitis associated with sarcoidosis, but its sensitivity is relatively low. In this study, we investigated whether serum soluble interleukin-2 receptor (sIL-2R) is also useful as a diagnostic marker, in addition to ACE, in the detection of uveitis associated with sarcoidosis.

Patients and methods: Data were analyzed from 126 patients with uveitis (52 sarcoidosis and 74 non-sarcoid uveitis) and 12 with primary intraocular lymphoma (PIOL) who had their serum sIL-2R and ACE levels measured.

Results: Serum sIL-2R level was elevated in 69.2% of patients with sarcoid uveitis, 5.4% of those with non-sarcoid uveitis, and 16.7% of those with PIOL. The sensitivity and specificity of an elevated sIL-2R level for the detection of sarcoidosis were 69.2% and 93.0%, respectively. In contrast, serum ACE levels were elevated only in patients with sarcoid uveitis, with a sensitivity of 44.2% and specificity of 100%. Furthermore, serum sIL-2R and/or ACE level was elevated in 75.0% of patients with sarcoid uveitis, which is higher than those who had elevated serum ACE level only (44.2%, P = 0.0025). The sensitivity and specificity of elevated sIL-2R and/or ACE in detecting sarcoid uveitis were 75.0% and 93.0%, respectively. The PPV was 0.87, and the NPV was 0.86.

Conclusion: Compared with the sensitivity of serum ACE levels alone, combined measurement of both serum sIL-2R and ACE levels improves sensitivity in the detection of uveitis associated with sarcoidosis. Nevertheless, serum ACE alone remains useful thanks to its high specificity in the differentiation of uveitis patients, with sarcoidosis from those without sarcoidosis.

Keywords: ACE; PIOL; angiotensin-converting enzyme; primary intraocular lymphoma; sIL-2R; sarcoid uveitis; soluble interleukin-2 receptors.