HBsAg

例句：

1. 1. The patient's HBsAg test came back positive, indicating he had been exposed to the virus.
   患者的乙型肝炎表面抗原检测呈阳性，表明他曾经接触过该病毒。
2. 2. The doctor advised the patient to avoid contact with people who have HBsAg, asit could increase his risk of infection.
   医生建议患者避免与携带乙型肝炎表面抗原的人接触，因为这可能会增加他的感染风险。
3. 3. The research found that HBsAg is a reliable indicator for detecting hepatitis B infections.
   研究发现，乙型肝炎表面抗原是检测乙型肝炎感染的可靠指标。