Chronic infection with hepatitis B virus (HBV) is a major global health problem [1]. The conversion rate of HBsAg with existing anti-HBV drugs is not high. In this paper, we observed the clinical characteristics of HBsAg conversion cases by using pegylated interferon α-2a in the treatment of chronic hepatitis B, and analyzed the relevant factors affecting the conversion of HBsAg. Data and methods I. Study subjects The study subjects were all patients with chronic hepatitis B who were hospitalized with pegylated interferon α-2a (180ug, once/week) antiviral therapy during the period from January 2005 to December 2008 in our hospital, a total of 84 cases. After the survey, the patients with missing or incomplete treatment and poor compliance were removed, and a total of 61 patients were finally enrolled in the database, and the antiviral treatment course was 1 year, among which 5 cases (8.2%) had HBsAg conversion and 56 cases did not. (a) A self-administered questionnaire containing 30 items was used. The questionnaire contains four aspects: clinical symptoms (fatigue, poor appetite, etc.), influencing factors (including age, gender, family history, antiviral history, history of HBsAg positive disease, history of abnormal liver function, etc.), laboratory indexes (HBVM titer, HBV DNA titer, CD4, CD4/CD8, etc.), and treatment (dose, duration of treatment, clinical and laboratory regression, etc.). It has good practicality and operability in clinical use. (b) Serum hepatitis virus markers were detected by microsomal enzyme immunoassay (Abbott reagent provided by Abbott); HBV DNA quantification was detected by fluorescence quantification-polymerase chain reaction (reagent provided by Roche), and the results were judged according to the external reference standard curve, and < 103 copies/ml was considered negative. The mean copy number of DNA (copies/ml) was calculated by the logarithmic mean method; HBV genotyping PCR microplate nucleic acid hybridization ELISA kit was performed according to the instructions, and CD4 count was performed by FACS Calibur flow cytometer with Mutiset automatic software for result analysis. III. Follow-up and statistics The data of 61 selected chronic hepatitis B patients were entered into an Excel database, including demographic information such as gender, age, occupation, home address, contact phone number, and clinical manifestations, diagnosis and treatment. The patients were followed up one by one for HBVM titer, HBV DNA titer, CD4, CD8 absolute count, side effects of antiviral therapy, and disease regression before and after treatment. Follow-up visits yielded additional information to complete the Excel database. Data were entered into SPSS 11.5 statistical analysis software for statistical analysis. The chi-square test was used for comparison between groups of count data, and logistic regression was used for multi-factor correlation analysis. Results I. Sex ratio and age composition The ratio of men to women in the HBsAg-converted group was 1.5:1, and the ratio of men to women in the HBsAg-not-converted group was 1.57:1; there was no significant difference in the sex composition ratio between the two groups (P > 0.05). The maximum age of the HBsAg-converted group was 32 years, the minimum age was 14 years, and the mean age was 25.5 years (25.5±7.5 years). the maximum age of the HBsAg-unconverted group was 47 years, the minimum age was 20 years, and the mean age was 35.7 years (35.7±8.3 years). significant, so it is considered that the age of HBsAg conversion group is younger than that of HBsAg non-conversion group. Second, the relationship between HBV genotype and the occurrence of HBsAg conversion by pegylated interferon alpha-2a treatment Five cases in the conversion group and 20 cases in the non-conversion group were extracted from the reserved sera for HBV genotype testing.