pregnancy tests

• 1. antibodies complimentary to hCG protein are bound to a coloured bead
• 2. hCG in urine binds to the antibodies
• 3. urine moves up the strips carrying beads
• 4. immobilised antibodies which bind to hCG create the first blue line
• 5. immobilised antibodies which bind to coloured beads create a second blue line if hCG is present