Here is some info about CA 19 which is a tumour marker, obtained through a blood test,
CA 19-9 is not sensitive or specific enough to use as a screening test for cancer, and it is not diagnostic of a specific type of cancer. Its main use is as a tumor marker:
To help differentiate between cancer of the pancreas and other conditions, such as pancreatitis
To monitor a person's response to pancreatic cancer treatment and/or cancer progression
To watch for pancreatic cancer recurrence
CA 19-9 can only be used as a tumor marker if the cancer is producing elevated amounts of it. Since CA 19-9 is elevated in about 65% of those with bile duct (hepatobiliary) cancer, it may be ordered to help evaluate and monitor people with this type of cancer.
When is it ordered?
CA 19-9 may be ordered along with other tests, such as carcinoembryonic antigen (CEA), bilirubin, and/or a liver panel, when a person has symptoms that may indicate pancreatic cancer. Those symptoms include abdominal pain, nausea, weight loss, and jaundice.
If CA 19-9 is initially elevated in pancreatic cancer, then it may be ordered several times during cancer treatment to monitor response and on a regular basis following treatment to help detect recurrence.
CA 19-9 may sometimes be ordered when a doctor suspects hepatobiliary cancer and/or bile duct obstruction. Non-cancerous causes of bile duct obstruction can cause very high CA 19-9 levels, which fall when the blockage is cleared. In these cases, it is a good idea to wait at least a week or two after the blockage is removed to re-check CA 19-9 levels.