SERPINA7 and cyclic hematopoiesis: Various strategies to screen for CH are being used (measurement of TSH (only), TSH + thyroxine (T4) or Free T4 (FT4), or T4-reflex TSH-reflex thyroxine binding globulin (TBG)), but the most used method is a single TSH measurement in a dried-blood spot (DBS) collected by a heel-prick on a filter paper card after 24 to 72 h of life.