sugar chain antigen 242

The carbohydrate antigen CA242 (CA242) is a monoclonal antibody raised from the human colorectal cancer cell line COLO205, and is also a sialylated glycosphingolipid antigen, which is co-expressed with CA50. Its biochemical nature is a sialylated carbohydrate structure, which belongs to mucin. It is present in normal pancreas and colonic mucosa, but its expression is extremely low. The sugar chain antigen CA242 is a tumor marker of the digestive system, especially pancreatic cancer and colorectal cancer. This indicator is significantly elevated in patients with pancreatic cancer and colorectal cancer. Its Cutoff value is generally 20 KU / L, the detection rate of malignant tumors can reach 60--85%, and the content is higher. In addition, this index will also increase in some patients with gastric cancer. Basic Information Specialist classification: Oncology examination classification: immune examination Applicable gender: whether men and women apply fasting: fasting Reminder: Specimens should be taken in duplicate, the average value is taken, and the corresponding antigen concentration is detected on the standard curve. Normal value The carbohydrate antigen CA242 (CA242) <12 kU/L. Clinical significance (1) Serum CA242 levels in lung cancer patients were significantly increased. CA242 levels were positively correlated with clinical stage, mass size and lymph node metastasis, and CA242 levels were significantly higher in lung adenocarcinoma than in squamous cell carcinoma and small cell lung cancer. CA242 decreased significantly after surgery and increased again after recurrence. CA242 has certain diagnostic value for lung adenocarcinoma. Dynamic observation of CA242 content has certain clinical significance for the monitoring of disease, efficacy evaluation and prognosis of lung cancer patients. (2) The increase of serum CA242 level can also be seen in malignant tumors such as gastric cancer, pancreatic cancer, colorectal cancer and ovarian cancer, and serum CA242 detection is helpful for the disease monitoring, efficacy evaluation and prognosis of the above tumors. (3) In patients with chronic colitis, chronic pancreatitis, cholecystitis and gallstones, serum CA242 levels may also be elevated, but the positive rate is lower. High results may be diseases: lung cancer, colorectal cancer, pancreatic cancer, ovarian cancer, gastric cancer (1) The positive rates of pancreas, colorectal, liver and gastric cancer were 86.6%, 62%, 44.9% and 34.60%, respectively. (2) The false positive rate of normal people is 4%. Inspection process The method is divided into three steps, namely antigen-antibody reaction, B and F separation, and radioactivity determination. (1) Reaction of antigen with antibody: The specimen (non-labeled antigen), labeled antigen and antiserum are sequentially dosed into a small test tube, and allowed to stand at room temperature (15 to 30 ° C) for 24 hours to fully compete for binding. (2) Separation of B and F: There are various separation techniques, and the precipitation method is commonly used. 1 second antibody precipitation method: also known as diabody method, after the test antigen specifically reacts with the first antibody, the corresponding second antibody is added, so that the formed antigen-first antibody-second antibody complex is co-precipitated. The labeled antigen B is separated from the free antigen F by centrifugation. This method is a specific precipitation, complete separation, low non-specific binding. However, the amount of the second antibody is large and the cost is high. In addition, the serum concentration and the presence or absence of anticoagulants can affect the results to some extent. 2 Polyethylene glycol (PEG) precipitation method: the protein is in an isoelectric point state, and the hydration layer is destroyed to cause protein precipitation. The advantage of this method is that PEG is convenient to prepare, inexpensive, and rapid to separate. The disadvantage is that there are many non-specific precipitates and the separation is incomplete. 3Second antibody-polyethylene glycol precipitation method: This method not only has the advantage of rapid precipitation of PEG method, but also maintains the effect of specific precipitation of second antibody, reduces the amount of second antibody, and reduces the concentration of PEG, so that non-specific precipitation Reduced material. 4 Activated carbon adsorption method: the free part of small molecules is adsorbed by the surface activity of activated carbon. For example, a layer of dextran is coated on the surface of the activated carbon to make a mesh having a certain pore diameter on the surface, thereby allowing small molecules of free antigen or hapten to escape and being adsorbed, while the macromolecular complex is excluded. After the antigen and the antibody are reacted, the dextran-activated carbon is added and allowed to stand for 5 to 10 minutes, so that the free antigen is adsorbed on the activated carbon particles, and the particles are precipitated by centrifugation, and the supernatant contains the labeled antigen. (3) Determination of radioactivity: After separation of B and F, the radioactivity can be measured. There are two types of measuring instruments: a liquid scintillation counter (measuring beta rays) and a crystal scintillation counter (measuring gamma rays). The unit of counting is the number of electrical pulses output by the detector in units of cpm (number of pulses/min). A standard curve is required for each measurement, and the different concentrations of the standard antigen are plotted on the abscissa, and the corresponding radioactivity measured is plotted on the ordinate. The radioactivity may be optionally B or F, and the calculated values ​​B/B+F, B/F or B/B0 may also be used. Specimens should be determined in duplicate, the average value is taken, and the corresponding antigen concentration is detected on the standard curve. Not suitable for the crowd There is no inappropriate crowd. Adverse reactions and risks It is a safe check and is harmless to the body.

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