Serum soluble interleukin-2 receptor measurement in patients with sarcoidosis: a clinical evaluation

To date, insufficient evidence is available to recommend serum soluble interleukin-2 receptor (sIL-2R) measurement as a routine test in the assessment of sarcoidosis. Therefore, we evaluated the clinical value of this test.

Forty-seven patients with sarcoidosis, all presenting with active disease, were included in the study. Initial serum sIL-2R levels were determined by enzyme-linked immunosorbent assay, and clinical data at presentation and follow-up were collected retrospectively.

The median follow-up period of all patients was 44 months (range, 6 to 100 months), and 38 patients had follow-up data present over at least 24 months. The median sIL-2R level was 1,068 U/mL (range, 248 to 4,410 U/mL; upper limit of normal, 710 U/mL). A positive correlation was found between serum sIL-2R levels and the number of CD4+ T lymphocytes in BAL (rs = 0.53, p < 0.001). In accordance with this result, both sIL-2R level and the number of CD4+ T lymphocytes were elevated in stage I compared to stage III disease (p < 0.05). Patients with extrapulmonary disease (ED) [excluding Löfgren's syndrome] showed higher sIL-2R levels than those presenting with only pulmonary sarcoidosis (p = 0.001). No relation was found between sIL-2R level and response to treatment, and there was no association between sIL-2R levels and radiographic evolution and lung function outcome.

Our data suggest a role for serum sIL-2R as marker of pulmonary disease activity and ED in patients with sarcoidosis.