Question: How do you detect the diseases? W

Alena Pance answered on 17 Jun 2020:

Hi Janmarco, there are various detection methods. In the case of an infectious disease, the organism can be tested for directly by detecting its DNA. The technique is called PCR and basically it makes millions of copies of a fragment of the infectious agent’s DNA. So this type of test tells us whether the organism is in the person, this is the kind of test used for covid-19 in fact.
Another way is to test for antibodies against the infectious organism. As these antibodies are the result of an immune response against the organism, the test tells us whether the person has had the disease, not necessarily whether they have an active infection at the time of testing. For this type of test, an extract of the organism or a specific molecule from it is fixed to a well in a sample plate, made to react with serum from the individuals to be tested. If there are antibodies in the serum, they will bind the extract in the plate and this interaction is then revealed by a reagent that changes colour.
A similar test can be used to detect other molecules from the infectious agent, again showing whether it is present in the patient or not.
These techniques can be applied to other diseases as well, mutations in the DNA causing disease for example can be detected by PCR, there are molecules specific to cancer that can be detected by the second method above called ELISA.