Measurement of Urinary S100B Protein Concentrations for the Early Identification of Brain Damage in Asphyxiated Full-term Infants

Background: Perinatal asphyxia is a major cause of mortality and morbidity. To date there are no reliable methods to detect which infants will develop brain damage after asphyxia insult. We investigated whether measurements of urine levels of S100B in asphyxiated full-term newborns may be a useful tool for early detection of post-asphyxia brain damage. Methods: A prospective study of 38 infants with perinatal asphyxia and 96 control subjects, recruited at 3 tertiary departments of neonatology between April 1, 1999, and July 31, 2001. Routine laboratory variables, neurologic patterns, and urine concentrations of S100B protein were determined at 4 predetermined time points (first urination and 12, 24, and 72 hours after birth). The concentrations of S100B protein in urine were measured using an immunoluminometric assay. The results were correlated with the presence or absence of neurologic abnormalities at age 12 months. Results: S100B protein levels were significantly higher in samples collected at all monitoring times from newborns with abnormal neurologic findings on follow-up (first urination, 1.92±0.33 μg/L; 12 hours, 2.78±1.71 μg/L; 24 hours, 4.75±4.08 μg/L; 72 hours, 5.93±1.63 μg/L) than in samples from those without (first urination, 0.24±0.06 μg/L; 12 hours, 0.13±0.06 μg/L; 24 hours, 0.21±0.07 μg/L; 72 hours, 0.12±0.04 μg/L) or from healthy infants (first urination, 0.11±0.01 μg/L; 12 hours, 0.12±0.03 μg/L; 24 hours, 0.12±0.02 μg/L; 72 hours, 0.12±0.02 μg/L) (P<.001 for all). An S100B concentration cutoff of 0.28 μg/L at first urination had a sensitivity of 100% and a specificity of 87.3% for predicting the development of abnormal neurologic findings on follow-up. The sensitivity and specificity of measurements obtained between 12 and 72 hours were up to 100% and 98.2%, respectively. Conclusion: Longitudinal S100B protein measurements in urine soon after birth are a useful tool to identify which asphyxiated infants are at risk of long-term neurologic sequelae.