Anti Saccharomyces Cerevisiae Antibody (ASCA) IgA

Anti-Saccharomyces cerevisiae antibodies (ASCA) are protein molecules present in people with inflammatory bowel disease (IBD). This disease involves several problems like significant inflammatory reactions, chronic symptoms, autoimmunity, and tissue damage.

ASCA test detects the presence of antibodies in blood because S. cerevisiae is a common yeast present in almost every food item. The ASCA blood test differentiates between Crohn’s disease and ulcerative colitis because it is difficult to assess the condition using biopsies.

Nearly 75% of people who have Crohn’s disease have ASCA in their blood and it could be either IgG or IgA. Since both Crohn’s disease and ulcerative colitis are intestinal disorders, they have similar symptoms and it gets confusing to start the treatment without proper testing.

While IgA is the first line of defence and indicates the presence of the condition in the body, IgG indicates the severity of the infection. The test also helps in finding out the type of IBD one has.

Furthermore, image diagnosis, endoscopic examination, and pathological tests fail to give a clear diagnosis of the condition. The ASCA test does not confirm the presence or absence of IBD, instead helps in differentiating two different conditions associated with bowel inflammation.

The symptoms of the condition may vary from one person to the other. Below are some common symptoms of IBD:

• Abdominal cramps and severe pain
• Diarrhoea with traces of blood 
• Sudden urgency to go to the restroom due to irregular bowel movements
• Unexplained weight loss
• Fever
• Loss in appetite 
• Anaemia due to iron deficiency 
• Joint pain
• Delayed growth in children
• Organ-related symptoms

At Apollo 24|7, the ASCA test involves the ELISA technique which is an accurate analysis of antibodies in the body.

It takes place on a 96-well plate to avoid separate replication of the experiment. The immunoassay also observes the interaction between antigen and antibody and looks for any specific reaction.

It uses many enzymes like horseradish peroxidase, alkaline phosphatase, and beta-galactosidase. However, the key players in the reaction are antigen and antibody only. The immobilized antigen on the 96-well plate captures the primary antibody.

The next step is the identification of the captured antibody using a secondary antibody. A secondary antibody is usually a colour-producing substance that changes the colour of the mixture.

Therefore, the ELISA plate is exposed to ultraviolet rays of a specific wavelength and the intensity is read using the spectrophotometric technique. The higher the intensity of colour, the more the concentration of antibodies. If there are more antibodies present in the blood, it indicates the severity of the reaction.

Some of the advantages of going for an ELISA test are:

• It is a simple procedure
• The sensitivity of the procedure is very high and the test is very specific
• The process is very efficient provided there is no manual error
• Safe and eco-friendly option
• Each assay is cost-effective even though it takes a little more time 
   

Medically reviewed by Dr. P Siva Charan Reddy, Surgical gastroenterologist, Apollo Hospitals Jubilee Hills, Hyderabad.

Frequently asked questions

What does the ASCA test result indicate?

The results of the ASCA blood test and pANCA test are interpreted together to confirm or rule out the specific condition. A positive ASCA test only confirms the presence of an IBD and does not indicate anything else. Additionally, if the ASCA test is positive and the pANCA test is negative, the person is most likely to have Crohn’s disease. On the other hand, if the ASCA test is negative and pANCA is positive, the person may be suffering from ulcerative colitis. Finally, a negative result in both tests rules out the presence of an IBD.

What could alter the results of an anti-saccharomyces cerevisiae antibody test?

The ELISA test is highly sensitive and any discrepancies in the preparation of antibodies could lead to improper results. In addition to this, the process is tedious and vulnerable to manual error. Hence, one can get false positive or false negative results easily.

How many times should one go for an ASCA blood test?

Anti-saccharomyces cerevisiae test is needed only once to distinguish between Crohn’s disease and ulcerative colitis. Usually, the test panel looks for both the classes of antibody i.e. IgA and IgG. However, if the earlier test included only one of the antibodies, then another round of tests may be required.

Are any special preparations required for the ASCA blood test?

No. The test does not require any special prior preparation.

How is an ASCA blood test useful?

An ASCA test is useful only for detecting the levels of antibodies and differentiating between the two intestinal conditions. However, the test does not help in monitoring the condition and cannot identify the severity of the disease.

Are there any risks associated with the ASCA blood test?

No. The ASCA blood test does not involve any risk because it is a simple blood test. However, if you have a unique blood disorder, you must be careful after the blood collection process.