back-to-back test
6.Methods:A drop of plantar blood from newborns 72 hours after delivery was obtained to put onto a filter paper and make it dry to test blood levels of TSH by ELISA method at former 4 years and by EIA method at later 6 years respectively. The test results were regarded as positive when TSH value ≥10 mIU/L by EIA or TSH value≥20 mIU/L by ELISA, and great majority positive cases were called back for diagnosis test.

