That's right, these tests can only give a positive result when using the beta subunit. But they don't always work correctly either.
Yesterday I tested the beta subunit using a pregnancy test and the test showed a negative result.
At very high concentrations of HCG/ml, the test may give a negative result. This phenomenon is called the hook effect. It occurs when the HCG level is so high that it exceeds the sensitivity threshold of the test. As a result, the test is not able to correctly identify the hormone and shows a false negative result.
The mechanism of the "hook" effect. At very high concentrations of HCG, hormone molecules begin to saturate both the test and control zones of the test, blocking the normal binding of antibodies, which leads to an incorrect interpretation of the signal by the test. Thus, the test cannot correctly "read" the presence of HCG, and instead of a positive result, a weak second line may appear or be absent altogether.
