Serum 1,25(OH) 2 Vitamin D and 25(OH) Vitamin D Ratio for the Diagnosis of Sarcoidosis-Related Uveitis.

Purpose : The diagnostic workup of uveitis is challenging, with 30 to 50% of cases remaining of undetermined etiology despite multiple investigations. Sarcoid granuloma-related increase of 1,25(OH) ₂ D levels could be helpful for the diagnosis of ocular sarcoidosis. Methods : Monocentric retrospective cohort study of patients for whom serum 25(OH)D and 1,25(OH) ₂ D levels were measured during the etiologic workup of unexplained uveitis in a tertiary referral center. The diagnoses of uveitis' underlying diseases were established according to international diagnostic criteria. Results : Fifty-nine patients were included. The diagnosis of defined, presumed or probable sarcoidosis was made in 37% of patients while 41% of cases remained of undetermined origin. The median serum levels of 25(OH)D in patients with ocular sarcoidosis and in those with uveitis due to another cause were 34.50 [21.2-40.8] and 43.20 [32.2-58.3] nmol/L (P=0.02), respectively. In the same subgroups of patients, the median serum levels of 1,25(OH) ₂ D were 132.4 [107.4-163.9] and 108.0 [84.30-130.5] pmol/l (P=0.02), and the median 1,25(OH) ₂ D/25(OH)D ratio was 4.17 [3.11-5.09] and 2.56 [1.54-3.37] (P=0.0007) respectively. A 1,25(OH) ₂ D/25(OH)D ratio >3.5 was associated with the diagnosis of sarcoidosis with a 68 % sensitivity and a 78% specificity and, in univariate analysis, was associated with an abnormal chest CT-scan (OR=5.7, P=0.003), granulomas on bronchial biopsy (OR=14.7, P=0.007) and bronchoalveolar lavage fluid lymphocytosis (OR=12.4, P=0.0006). Conclusion : The measurement of serum 25(OH)D and 1,25(OH) ₂ D levels is a useful tool in the etiological workup of patients with unexplained uveitis, since a high 1,25(OH) ₂ D/25(OH)D ratio is suggestive of ocular sarcoidosis.