Thymus size in infants from birth until 24 months of age evaluated by ultrasound. A longitudinal prediction model for the thymic index.

To do a follow-up sonography assessment of the thymic size in infants at an age of 24 months, and to create a longitudinal prediction model for the thymic index covering all ages from birth to 24 months.Of 37 infants examined in an earlier investigation, 34 attended a 24-month follow-up examination. The thymic index, a volume estimate, was assessed by sonography and compared to clinical variables, breast-feeding status and illness. The longitudinal prediction model was based on data throughout 2 years.There was no significant relation between the thymic index and the clinical variables, breast-feeding status or illness at 24 months. An overall test for the effect of breast-feeding status at 4 months for infants from 0-24 months was significant, as was the actual body length of the infants from 0-8 months. Prediction models were estimated.Based on a 24-month longitudinal sonography study, prediction models are presented whereby the thymic size, as an index, can be predicted at all times from birth to 24 months of age.