Utility of Screening Investigations for Systemic Sarcoidosis in Undifferentiated Uveitis

Purpose: To establish the utility of screening investigations for systemic sarcoidosis in a large cohort of subjects presenting with undifferentiated uveitis.

Design: Evaluation of a diagnostic test.

Methods: Retrospective review of consecutive subjects presenting to Auckland District Health Board with undifferentiated uveitis who underwent screening for sarcoidosis.

Results: Seven hundred nine subjects were included in the study. Systemic sarcoidosis was identified in 10.7%, and was biopsy proven in 43.4%. Sensitivity and specificity were highest for computed tomography (CT) of the chest (98.0% and 100%) and for chest radiograph (CXR; 57.6% and 100%). Serum ACE was elevated in 43 subjects, of whom 29 (67.4%) had systemic sarcoidosis. Sensitivity of serum ACE was 38.2% and specificity 97.8%, with an area under the curve (AUC) of 0.801. Lymphopenia was observed in 40 subjects, of whom 18 (45.0%) had systemic sarcoidosis. Sensitivity of lymphopenia was 23.7%, with specificity 96.5% and AUC 0.761. All subjects with elevated ACE and lymphopenia had evidence of systemic sarcoidosis. Biopsy was performed in 50 subjects, positive in 33 subjects (66.0%). Mediastinal biopsy was the most frequent (26 subjects). Skin biopsy was performed in 11 subjects (positive in 8). Only 1 subject with a positive skin biopsy had elevated ACE, lymphopenia, and bihilar lymphadenopathy on CXR.

Conclusions: Sensitivity and specificity were highest for chest CT. Although CXR had excellent specificity, CXR screening alone would still miss many cases of sarcoidosis. Combined elevated ACE and lymphopenia were strongly suggestive of systemic sarcoidosis, and biopsy of skin lesions may detect patients otherwise missed by routine screening tests.