The molecular test, also called the PCR, the RNA or molecular nasopharyngeal swab is currently the most reliable for diagnosis of coronavirus infection.
Here is a list of private centers that do the molecular test.
Here is the contact information for Campus Biomedico (where you can do the test without a prescription, paying with a credit card on the spot)
The antigen test (antigen nasopharyngeal swab, or rapid swab test) is a first-level diagnostic tool.
The blood test or antibody test is a diagnostic test based on the identification of IgH antibodies in the blood.
Any negative result of this test does not in any way indicate immunity to the virus.
In case of a positive result of the blood test, it’s necessary to promptly carry out a rhino-pharyngeal swab to ascertain if the infection is active and if there is a risk of infecting others.
Practically all laboratories, public and private, are qualified to carry out the blood test.
Here you can find the pages of the Lazio Region where the characteristics of these three tests are described in detail.