We have developed a blood spot assay for thyroid stimulating hormone (TSH) based on the Amerlite TSH-30 serum assay for use in the Welsh neonatal hypothyroid screening programme. A total of 67 656 infants were screened in 1994 and 1995, and 28 cases of primary hypothyroidism were detected, giving a prevalence of one in 2416. The method is sensitive and rapid, results being available within 3 h of receipt of samples. The assay enables much faster detection of primary hypothyroidism than was previously possible, and therefore contributes to earlier treatment of affected infants.
