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Carbohydrate antigen CA 19-9 in blood
Last reviewed: 05.07.2025
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Reference values (norm) of CA 19-9 in blood serum are up to 37 IU/ml. Half-life is 5 days.
CA 19-9 is a glycoprotein found in the fetal epithelium of the pancreas, stomach, liver, small and large intestines, and lungs. In adults, this antigen is a marker of the glandular epithelium of most internal organs and a product of their secretion. It should be taken into account that the antigenic determinant of the CA 19-9 antigen and the Lewis blood group Ag (Le(ab-) are encoded by one gene. This gene is absent in 7-10% of people in the population. Accordingly, such a number of people genetically lack the ability to synthesize CA 19-9, therefore, even in the presence of a malignant tumor from the glandular epithelium, the level of the marker in the blood serum is not determined or its concentration is at very low values. CA 19-9 is excreted exclusively with bile, therefore, even minor cholestasis can cause a significant increase in its level in the blood. An increase in the concentration of CA 19-9 (up to 100 IU/ml and even up to 500 IU/ml) can also be observed in benign and inflammatory diseases of the gastrointestinal tract (in 50% of cases of pancreatitis) and liver (hepatitis, cirrhosis), in cystic fibrosis and inflammatory diseases of the pelvic organs in women (in 25% of cases of endometriosis and uterine fibroids). In these groups of patients, CA 19-9 can be used as a marker for monitoring the treatment of these diseases.
As a tumor marker for pancreatic carcinoma, CA 19-9 has a sensitivity of 82%. No correlation was found between the marker concentration and tumor mass. However, its level above 10,000 IU/ml indicates the presence of distant metastases. A dynamic study of the CA-19-9 level provides valuable information for assessing the effectiveness of surgical treatment and determining the prognosis. With a low level of CA-19-9 in the blood (64-690 IU/ml), life expectancy is on average 17 months, at a level of 75-24,000 IU/ml - 4 months. CA 19-9 has a sensitivity of 50-75% in hepatobiliary carcinoma. Currently, CA 19-9 is the second most important marker (after CEA) for diagnosing gastric carcinoma. Its increase is observed in 42-62% of patients with gastric cancer. The sensitivity of CA 19-9 is:
- in patients with pancreatic cancer - 82% with a cutoff point of more than 80 IU/ml;
- in patients with liver cancer - 76% with a cutoff point of more than 80 IU/ml;
- in patients with gastric cancer - 29% with a cutoff point of more than 100 IU/ml;
- in patients with colorectal cancer - 25% with a cutoff point of more than 80 IU/ml.
Determination of the content of CA 19-9 in blood serum is used:
- for diagnosis and monitoring of treatment of pancreatic cancer;
- for early detection of pancreatic tumor metastasis;
- for monitoring colon, stomach, gallbladder and bile duct cancer;
- for diagnosis and monitoring of treatment of ovarian cancer (in combination with CA-125 and CA 72-4).
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