Introduction to ELISA and Its Applications in Pregnancy Tests

ELISA stands for Enzyme-Linked Immunosorbent Assay. It's a plate-based assay technique for detecting and quantifying substances such as peptides, proteins, antibodies, and hormones.

Sandwich ELISA uses two antibodies specific to the target antigen. Capture antibodies coated on the plate bind the antigen; a detection antibody forms the 'sandwich'. An enzyme-linked secondary antibody provides the signal.

The enzyme linked to the detection antibody reacts with a substrate to produce a measurable product. The reaction's intensity correlates with antigen levels, allowing for precise quantification.

Home pregnancy tests detect human chorionic gonadotropin (hCG) in urine. When pregnant, women produce hCG, which the test's antibodies are designed to capture and signal.

These tests utilize a sandwich ELISA format. A sample migrates via capillary action, allowing hCG to bind to immobilized antibodies. A secondary antibody with a color indicator reveals results.

Pregnancy tests are highly sensitive, detecting hCG levels as low as 25 mIU/mL. They're specific to hCG despite its structural similarity to other hormones, reducing false positives.

Digital pregnancy tests now incorporate microprocessors to interpret results, providing a clear digital display. They also store data, enabling tracking of hCG levels over time.