AFP testing is performed clinically by blood collection. The normal value of AFP measured by different techniques is slightly different: 1) enzyme immunoassay: normal value of AFP <25μg/L; 2) radioimmunoassay: normal value of AFP <20μg/L; 3) radioimmunoelectrophoresis: normal value of AFP <25μg/L. Regardless of which technique is used for AFP testing, if the value of AFP is >400μg/L, the normal value of AFP is less than 25μg/L. No matter which technique is used for the examination of methemoglobin, if the value of methemoglobin is >400μg/L, it is positive for high concentration of methemoglobin and needs to be paid high attention. The clinical significance of elevated AFP includes: 1. Pregnant women: AFP can be elevated to different degrees in pregnant women; 2. Viral hepatitis and viral hepatitis: AFP can also be detected to different degrees in patients with viral hepatitis and viral hepatitis, but the elevated level is often lower than that in patients with primary liver cancer; 3. Primary liver cancer: Elevated AFP can be used for the early diagnosis of primary liver cancer. If the value of methemoglobin is >400μg/L, or >200μg/L for 8 weeks, and the glutathione aminotransferase is normal, and pregnancy and germinal embryonic tumor can be excluded, the possibility of primary hepatocellular carcinoma is considered. Patients with primary hepatocellular carcinoma diagnosed by AFP and imaging need to have dynamic AFP level monitoring, which is very important to judge the efficacy of hepatocellular carcinoma treatment and assess the prognosis of patients. 4. Malignant tumors of gonads and embryonic tumors: Among malignant tumors of gonads and embryonic tumors, such as testicular carcinoma and teratocarcinoma, AFP can also appear to be significantly increased.