The ELISA

ELISA is stand for Enzyme-linked immunosorbent assay. It is an immunological or serological test to check antigen present in the serum. It have 2 types Direct ELISA or Sandwich ELISA Test and Indirect ELISA test. For Direct ELISA test, it is used to diagnose various microbial infections (such as HIV, Hepatitis A and C, Cholera Vibrio, Helicobacter pylori,...), cancer and other immunological disorders. Different from Direct ELISA, Indirect ELISA is used to diagnosed Hantavirus, rubella virus, toxoplasma....


Procedure of Sandwich ELISA

1. Pour known antigen of specific antibodies on well containing micro titer plate and wait for 2-3 hours or over night then wash with buffer to remove unbound antibodies. 
2. Add patient serum specimen on the well and wait for 1-2 hours and then wash with buffer. 
3. Add Enzyme labelled (linked or conjugated) antibodies on the well and wash with buffer. 
4. Finally, add the substrate (colorless substance) on the well and wait for 1-2 hours to observe the reaction.

Result: if the color develops confirm Positive.
            if no color develops confirm Negative.


Procedure of Indirect ELISA

1. Add unknown amount of specific antigen on the micro titer well and wait for 2-3 hours followed by wash with buffer. 
2. Add patient serum on the well and wait for 1-2 hours then wash with buffer. 
3. Add enzyme labelled anti-antibody and wait for 1-2 hours followed by wash with buffer. 
4. Add substrate and observe the color change. 

Result: Positive: Color develops
            Negative: No color develops.