Table 2.
Diagnostic performances of the main biomarkers available in ocular sarcoidosis.
| Biomarker | Test Performance/Usefulness | Limitations/Comments | References | ||
|---|---|---|---|---|---|
| Lymphopenia (lymphocyte count <1000/mm3) * | Se/Sp | PPV/NPV | YI/AUC | Poor Youden’s index. Test performances based on lymphocyte count cutoff. Better performance coupled with serum ACE. | [43] |
| 0.15/0.97 | 0.48/0.85 | 0.12/0.71 | |||
| Increased sensitivity (0.19), specificity (0.99) and NPV (0.90) when associated with elevated ACE. Increased sensitivity (0.75) but lower specificity (0.77) with 1470/mm3 cutoff. Easily accessible, simple, and non-invasive. | |||||
| Elevated ACE * (>52–61 UI/l) | Se/Sp | PPV/NPV | YI/AUC | Optimal cutoff varying from 52 UI/l to 61 UI/l. Uninterpretable if patient uses ACE inhibitors. | [43,44] |
| 0.45–0.78/0.9 | 0.44/0.89–0.97 | 0.35–0.68 | |||
| Highly specific and high NPV in patients referred for uveitis with no known cause. Increased sensitivity/specificity coupled with lymphopenia. | |||||
| sIL-2R (threshold according to manufacturer) | Se/Sp | PPV/NPV | YI | Not used widely enough (not validated in revised IWOS criteria). No validated threshold. | [45] |
| 0.98/0.94 | 0.77/0.99 | 0.92 | |||
| Very sensitive, high NPV, good YI. sIL2R levels replaced negative tuberculin skin test in Japanese diagnostic criteria for sarcoidosis. | |||||
| Lysozyme * | Sensibility: 0.60–78; sensitivity: 76–95. In systemic sarcoidosis, lysozyme levels are positively correlated with sIL-2R levels and ACE levels. | High lysozyme levels can be found in infectious uveitis (tuberculosis, syphilis). | [46,47] | ||
| Chitotriosidase activity | No data in sarcoidosis uveitis. In patients with systemic sarcoidosis, 48.8 nmol/h/mL cutoff is associated with 0.89 sensitivity and 0.93 specificity. | High chitotriosidase activity reported in other pulmonary diseases (COPD, asbestosis). Not easily available. | [48] | ||
Abbreviations: ACE: angiotensin converting enzyme; AUC: area under curve; COPD: chronic obstructive pulmonary disease; PPV/NPV: positive and negative predictive value; Se: sensitivity; Sp: specificity; YI: Youden index. * Biomarker included in the IWOS criteria.