What is the Difference Between Sandwich Elisa and Competitive Elisa

The key difference between sandwich Elisa and competitive Elisa is that sandwich ELISA is a type of ELISA commonly used to detect and quantify antigens in immunoassays, while competitive ELISA is a type of Elisa commonly used to detect and quantify antibodies in immunoassays.

Enzyme-Linked Immunosorbent Assay (ELISA) is an immunoassay technique that detects diseases. Sandwich and competitive ELISA are the two main types of ELISA used in diagnostics. The main types of ELISA include direct ELISA, indirect ELISA, sandwich ELISA, and competitive ELISA. Moreover, all of them require the use of fluorescent, chemiluminescent, or colorimetric tags. These tags are known as reporters and are used to quantify the assay.

CONTENTS

1. Overview and Key Difference
2. What is Sandwich Elisa
3. What is Competitive Elisa
4. Similarities – Sandwich Elisa and Competitive Elisa
5. Sandwich Elisa vs Competitive Elisa in Tabular Form
6. Summary – Sandwich Elisa vs Competitive Elisa

What is Sandwich Elisa?

Sandwich ELISA is a type of ELISA commonly used to detect and quantify antigens in immunoassays. It is a type of enzyme-linked immunosorbent assay that uses two antibodies: a capture antibody and a detection antibody. In this technique, the antigen in the sample is bound between the antibodies. The purpose of ELISA is to detect the presence of a target antigen in a sample. Therefore, in the case of sandwich ELISA, the target antigen is bound between a capture antibody and a detection antibody. At the beginning of the procedure, the capture antibody is already immobilized on the surface. However, the detection antibody is applied as the last step before quantification. The two antibodies in the sandwich ELISA bind to different places on the target antigen. Moreover, it is very important that the capture antibody and target antibody do not interfere with each other’s binding capabilities.

The steps in the sandwich ELISA include coating the surface with a capture antibody, blocking unbound protein binding sides on the surface, adding a sample containing target antigen, adding detection antibody labeled conjugate, and detection. The advantage of this technique is its high specificity and high sensitivity. However, its main disadvantage is the interaction between the capture and detection antibodies.

What is Competitive Elisa?

Competitive ELISA is a type of ELISA commonly used to detect and quantify antibodies in immunoassays. This is a technique that is also known as inhibition ELISA. In competitive ELISA, the sample antigen competes with a reference antigen for binding to a specific amount of labeled antibody.

The reference antigen is pre-coated on a surface of a multi-well plate. Then the sample antigen is pre-incubated with the labeled antibody added to the wells. Depending on the amount of antigen in the sample (more or less), free antibodies will be available to bind the reference antigen. The weaker signals indicate that less reference antigen will be detected when there is more antigen present in the sample. The advantages of this technique are suitability for the detection of small antigens, suitability for the detection of complex samples, high specificity, and high sensitivity. However, it has some disadvantages, such as the need for labelling antibodies for each ELISA, which may result in the inactivation of antibodies and signal decrease as the target antigen increases.

What are the Similarities Between Sandwich Elisa and Competitive Elisa?

• Sandwich and competitive ELISA are the two main types of ELISA used in diagnostics laboratories.
• Both techniques use antigen-antibody interaction.
• These techniques use a fluorescent, chemiluminescent, or colorimetric tag called reporters.
• Both techniques are inexpensive.

What is the Difference Between Sandwich Elisa and Competitive Elisa?

Sandwich ELISA is commonly used to detect and quantify antigens in immunoassays, while competitive ELISA is commonly used to detect and quantify antibodies in immunoassays. Thus, this is the key difference between sandwich Elisa and competitive Elisa. Furthermore, sandwich ELISA uses two antibodies, while competitive ELISA uses two antigens.

The below infographic presents the differences between sandwich Elisa and competitive Elisa in tabular form for side-by-side comparison.

Summary – Sandwich Elisa vs Competitive Elisa

Sandwich and competitive ELISA are the two main types of ELISA used in routine disease diagnostics laboratories. Both techniques use antigen-antibody interaction and different tags as reporters. Sandwich ELISA is commonly used to detect and quantify antigens in immunoassays, while competitive ELISA is commonly used to detect and quantify antibodies in immunoassays. So, this summarizes the difference between sandwich Elisa and competitive Elisa.

Reference:

1. “Sandwich Elisa Protocol.” Abcam, 23 Mar. 2023.
2. Branch, Angie. “What Is a Competitive Elisa?” Echelon Biosciences, 27 July 2021.

Image Courtesy:

1. “Sandwich ELISA” By Cawang – Own work (CC0) via Commons Wikimedia
2. “ELISA or Lateral flow formats” By Ppresh.ant – Own work (CC BY-SA 4.0) via Commons Wikimedia