Neonatal thyroid screening--the Shifa experience

To evaluate the results of T4, TSH analysis and pattern of presentation in babies born at our hospital.

We retrospectively reviewed the data collected from T4, TSH screening on all babies delivered at our Hospital, where the blood was drawn within the first 4 days of life. Period under evaluation was from October 1995 to October 1998. Shifa Reference values were used.

Blood sample were collected from 997 babies within 4 days of birth. Nine hundred and forty nine (95.2%) were evaluated after 24 hours. and 48(4.8%) in less than 24 hours of age. A high TSH was reported on 166 (16.8%) babies and a low T4 was reported on 78 (7.9%) babies. Statistical analysis showed a similar sensitivity for T4 and TSH (100%) but a higher specificity for T4 (93.1%) as compared to TSH (86%). A high-TSH with a low T4 was reported in 5 (0.5%) babies out of which 1 case was confirmed as congenital hypothyroidism requiring permanent thyroxin replacement and one case manifested a picture consistent with transient hypothyroidism. A low TSH with a low T4 was seen in 2 cases, however, they were all premature babies on antibiotics.

Congenital hypothyroidism may be more frequent in our population and for the purpose of screening babies T4 values would carry a higher positive predictive value than TSH. Combining T4 TSH assays would however reduce the call back rate quite significantly but may prove to be a bit more expensive.