Lewis blood group antigen (CA19-9)
Biochemistry Overview / Directory
Purpose of the test
This assay uses the GI-MA monoclonal antibody which reacts specifically with the sialylated Lewis blood group antigen (CA 19-9). This antigen is expressed as a monosialoganglioside on secreted mucus glycoproteins, which has a molecular weight of approximately 10kDa. This protein which is designated CA 19-9 may be found to be elevated in the serum of patients with pancreatic and lungs cancers. It can also be elevated in the following malignancies, bile tract carcinoma, uterine adenocarcinoma, ovarian mucinous tumours, and liver metastases in the breast and lung. In the case of digestive tract carcinomas such as gastric or colorectal cancer CA 19-9 has been found to be a useful complement to CEA in the monitoring of treatment and the detection of sub-clinical recurrence. There is a rare incidence of patients with the blood group constellation Lewis (a-b-), who are unable to express CA 19-9 reactive determinants and so cannot have their malignancies monitored in this way.
Pancreatic cancer in the non-jaundiced patient can be difficult to diagnose, even with the aid of modern scanning techniques. The detection and quantification of CA 19- can be used in the serological diagnosis of the disease.
In a more general way, the measurement of CA 19-9 can be used to monitor the response of tumours to first-line therapy. A persistently rising CA 19-9 concentration suggests malignancy and a poor response to therapy, whilst the converse would tend to indicate a favourable response to the therapeutic regime.
Although useful as an adjunct in cancer diagnosis, it should not be considered a screening or diagnostic test when used alone.
Reference Range
Less than 37kU/L
Sample Requirements
Serum from a plain vacutainer (100 µL).
Storage and Transport
Stable at 4°C. Send by overnight first class post
Turnaround Time
The assay is run once a week
Price
Price available on application - please contact adrianturner1@nhs.net. Discounts could be available for significant workloads.
Contacts
Dr Hagosa Abraha
T 020 3299 4134
