S100 is a calcium-binding protein that consists of 2 subunits (alpha, beta) that may be present in various combinations:
(1) beta-beta (S100B)
(2) alpha-beta (S100A1)
(3) alpha-alpha
S100B and S100A1 are found in glial cells and some neurons.
The molecular weight for S100B is 21 kiloDaltons. The beta subunit has a molecular weight of 10.7 kiloDatlons.
Qian et al found that S100-beta was elevated in blood from the umbilical artery in neonates with HIE, with higher concentrations associated with more severe HIE. The cutoff distinguishing mild from moderate/severe HIE was 2.02 micrograms/L.
Gazzolo et al found that S100B protein in the urine could be monitored to identify neonates who are at risk for HIE.
(1) They found that a S100B > 0.41 micrograms/L in the first urine sample predicted HIE,.
(2) Elevated S100B in urine collected up to 72 hours after delivery was associated with HIE. Urine was suitable for monitoring an infant.
Points for clarificaton:
(1) The specimen as blood from umbilical artery or urine.
(2) The time of specimen collection relative to birth.
(3) Testing for S100B vs S100beta.
(4) Correction of urine measurement for variation in dilution, such as reporting as the ratio of urine S100B to urine creatinine.
