1. Antigen-Antibody Reaction:
* The strip contains a test line coated with antibodies specific to the target analyte (the substance being tested for).
* The control line is coated with antibodies that bind to a different part of the analyte or to a universal protein.
2. Sample Application:
* When you apply the sample (e.g., urine, blood) to the strip, the analyte in the sample will flow through the test strip.
3. Movement and Binding:
* The analyte in the sample will bind to the antibodies on the test line if it is present.
* Meanwhile, a colored conjugate (usually gold nanoparticles attached to an antibody) also moves through the strip.
* The conjugate binds to the analyte, forming a colored complex.
4. Visualization:
* If the analyte is present, the colored complex binds to the antibodies on the test line, creating a visible line.
* The control line always appears, indicating that the test has worked correctly.
5. Interpretation:
* The presence of a colored line on the test line confirms a positive result for the analyte.
* The absence of a line on the test line indicates a negative result.
Here's a simplified analogy:
Imagine a lock and key. The analyte is the key, the antibodies on the test line are the lock, and the colored conjugate is the key ring. When the key (analyte) fits the lock (antibody), the key ring (colored conjugate) attaches, creating a visible signal.
Common Applications of Strip Tests:
* Pregnancy tests
* Ovulation tests
* Drug tests
* Blood glucose monitoring
* Infectious disease testing
Advantages of Strip Tests:
* Easy to use
* Fast results
* Relatively inexpensive
* Portable
Limitations of Strip Tests:
* Can have lower sensitivity than other diagnostic methods
* Prone to false positive or false negative results
* May not be suitable for all analytes
Remember to always follow the manufacturer's instructions for using and interpreting strip tests.