Home » ‘Xanthurenic acid index’ is a reliable criterion for the deficiency of the vitamin Vitamins MCQs ‘Xanthurenic acid index’ is a reliable criterion for the deficiency of the vitamin January 26, 2022 17 Views Q. ‘Xanthurenic acid index’ is a reliable criterion for the deficiency of the vitamin A. Pyridoxal B. Thiamin C. Pantothenic acid D. Cobalamin Answer: Pyridoxal