Establishment of reference interval for cord blood TSH

Introduction: TSH values in the cord blood is useful for neonatal screening of thyroid disorders. Screening is essential to rule out congenital hypothyroidism in neonates without any physical signs. In South Indian population, the reference interval for cord blood TSH has not been established. Aim: To establish the reference interval of cord blood TSH in South Indian population. Methods and Material: This study was conducted at Dr. SMCSI Medical College, Karakonam, Trivandrum. 200 neonates were selected as reference individuals for cord blood collection. The rejection criteria were complications in the delivery or hypothyroidism in the mother or the neonate. TSH was estimated in the cord blood by chemiluminescence method in VITROS ECi. Statistical Analysis: The data obtained was analyzed using SPSS version 16. Paired T test was used for statistical analysis. The reference interval was determined by nonparametric method by taking middle 95 percentile. Correlation analysis was done using Pearson correlation coefficient. Results: The reference interval for cord blood TSH is 2.2 to 18 mIU/L. The results showed that there is no significant difference between male and female neonates as well as the normal and the Caesarean section. Correlation study showed that cord blood TSH level was independent of the gestational age. Hence subgroup reference interval was not required. Conclusions: The reference interval for cord blood TSH is from 2.2 to 18 mIU/L. Establishment of subgroup reference interval is not required since there is no significant variation between male and female neonates as well as between normal and caesarean section.