I. Clinical significance of tumor marker testing 1. early tumor screening For example, chorionic gonadotropin (HCG) has been successfully used for screening of choriocarcinoma, and the use of this marker has significantly reduced the mortality rate of patients with choriocarcinoma worldwide. It has a greater practical value in population screening. AFP screening is commonly used in African and Southeast Asian countries as a tool to screen for hepatocellular liver cancer in patients with hepatitis B. PSA has also been used in the screening of prostate cancer with the same effect. Therefore, the screening of tumor markers is of great value to the high-risk group. 2.Differential diagnosis after the appearance of tumor symptoms or suspicious masses When a patient is suspected to have a tumor, the detection of tumor markers is helpful to identify benign and malignant tumors. 3.Monitoring the efficacy, recurrence or metastasis and judging the prognosis is the most valuable role of tumor markers. The tumor markers are elevated before surgery and decreased after surgery, which indicates successful surgery; slightly decreased after surgery and then re-elevated, which indicates that the surgery is not effective; decreased after surgery and significantly increased after some time, which indicates tumor recurrence or metastasis. This indication often precedes the appearance of clinical symptoms by several months. After treatment, the rise and fall of tumor markers correlate well with patient outcome and prognosis. The decrease of tumor markers after treatment indicates that the treatment is effective; if the tumor markers continue to rise after treatment, the treatment plan should be changed, and if the tumor markers continue to rise, it often indicates recurrence or metastasis. An ideal tumor marker should have the following characteristics: (1) high sensitivity, which can detect all tumor patients at an early stage; (2) good specificity, which should be 100% accurate in identifying tumor and non-tumor patients; (3) organ specificity, which can localize the tumor; (4) serum concentration correlates with tumor size and clinical stage, which can be used to judge the prognosis; (5) half-life (5) short half-life, which can reflect the dynamic changes of tumor and monitor the treatment effect, recurrence and metastasis; (6) high precision and accuracy of the determination method, easy to operate and inexpensive kits. However, so far, there is not an ideal tumor marker. The reference value and reference range are verified by a large number of people in normal and non-tumor patients, not absolute values, and the reference value may be different for different people and different regions. The normal reference values are different for different age and population, for example, PSA increases with age. 3.Examinations and treatments may affect the accuracy of tumor marker detection. For example, PSA may increase after rectal examination, prostate puncture and prostate massage, and PSA production may be inhibited after anti-androgen therapy. 4. Preservation or contamination of specimens can affect the results. NSE is present in red blood cells, plasma cells and platelets, hemolysis or specimens left too long can cause NSE to rise. 5, different methods, different laboratory test results may have a certain degree of error. 6.If a certain tumor marker is found to be elevated during physical examination, such as significantly elevated, or symptomatic, it is recommended to have a comprehensive examination to exclude the possibility of related tumors. Otherwise, it should be rechecked at an interval of 2-4 weeks. If it is progressively elevated for 3 times in a row, it is recommended to have a comprehensive examination.