IFNA1 and sarcoidosis: The highest diagnostic accuracy for discriminating between sarcoidosis and TB was achieved by assessing serum IFN activity by measuring the induction of ten distinct ISG in THP-1 cells, and subsequently calculating an integrated IFN gene signature score (Youden's index = 0.74, sensitivity = 74 %, specificity = 100 %, and AUC = 0.900).