SONOGRAPHIC MEASUREMENT OF THYMIC SIZE IN HEALTHY NEONATES - RELATIONTO CLINICAL-VARIABLES

Purpose. To assess the variation in thymic size in healthy neonates by sonography and to study the possible correlation to clinical variable s. Material and Methods: A study was made of 149 healthy term infants, at less than one week of age. The size of the thymus was assessed by sonography as a volume estimate, the thymic index. This index was comp ared to sex, weight, length, gestational age, and level of perinatal a sphyxia of the infant. T-cell subsets (percentages of CD4 and CD8 rece ptor-positive T-lymphocytes in peripheral blood) were determined in 83 of the infants and compared to the sonographic thymic index. Results: The thymic index varied between 4 and 29, and was positively correlat ed to the weight of the infant (p=0.0003). There was no correlation to sex, length, gestational age or slight perinatal asphyxia. We found n o correlation between the size of the thymus and the CD4 percentage, t he CD8 percentage, or the CD4/CD8 ratio. Conclusion: The size of the t hymus in healthy neonates as measured by sonography is significantly c orrelated to the weight of the infant. For a given weight of an infant it is possible to predict the normal range of thymic size.