Liver function and HBV serology were tested in the hospital's clinical laboratory. HBV DNA was detected with a real-time PCR amplification kit (Kehua Biological Company, Shanghai, China), which can detect HBV DNA levels as low as 500 copies/ml. HBV markers were detected using ELISA kits (Abbot Laboratories, North Chicago, IL, USA) on an ARCHITECT i2000 automatic immunoassay analyzer (Abbott), in accordance with the manufacturer's instructions.
Hearing screenings were performed with the Echo-Screen (Madsen Company, Germering, Germany).
Peripheral blood samples were spotted onto filter paper, and the specimens were sent to the Beijing Neonatal Diseases Screening Center to rule out congenital phenylketonuria and hypothyroidism by liquid chromatography tandem mass spectrometry detection. Five types of congenital disease (hearing defects, congenital heart disease, congenital hip dislocation, congenital hypothyroidism, and phenylketonuria) were assessed.