Laboratory-specific studies have also been reported: second-tier 21-deoxycortisol screening for CAH [931]; a 4-step screening protocol for CF (IRT-PAP-DNA-EGA) [932]; a reevaluation of NBS for TYR-I using succinyl acetone in view of a late-diagnosed case (false negative) [933]; and the use of thyroxine-binding globulin concentrations to improve screening for central CH [934]. The gene discussed is C4B; the disease is cystic fibrosis.