TTR and vitamin A deficiency: When used in combination, RBP and transthyretin were better at discriminating between children with and without vitamin A deficiency than when transthyretin was used alone (AUC: 0.98 versus 0.96; P = 0.01) or when RBP was used alone (AUC: 0.98 versus 0.93; P = 0.001) (Figure 3).