I think you would need to contact each lab that offers the tests. Also, you need to be aware that the quantitative results change over time. My friend had Covid & was donating convalescent plasma each month. Her antibody levels were tested before each donation and at 6 months, the fell to undetectable.

May I ask why you are seeking a quantitative test?
Sue

The antibodies that show up in our blood are not the ones that we all want to know about and that is the number of antibodies (quantitative) that count for protection. If I'm wrong about what you are asking, I apologize.

The SARS-CoV-2 spike protein test is used to check for antibodies for the vaccines for Covid 19. It only shows whether there are antibodies in the blood, specifically IgM/IgG spike proteins which could be either from direct exposure to Covid-19 or from the vaccination. Having the antibodies is a good sign but it does nothing to directly tell us the level of our immunity to the virus.

Because of this the "quantitative (whereby the actual level of the antibody" can not be reported as there is no test as yet that has been approved for testing this, or perhaps in existence.
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https://www.labcorp.com/coronavirus-disease-covid-19/providers/antibody-test
There may be more than one type of antibody is involved (as is the case for flu, for instance) and they might not know if they exist at this time. There are many processes involved in testing the quantitative levels of antibodies and variants certainly change things. There just hasn't been enough time that has passed to answer this. This is a very simple answer to a very complex question and process. Perhaps @sueinmn has more information for you
https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/antibody-tests-guidelines.html
Does this make sense?

This is a question that you really need to have addressed by a physician or medical professional who is involved in this type of research, rather than on a chat board that is mainly answered by fellow patients. Each lab sets different parameters for the tests, and different thresholds for their results. Some tests are designed to be more sensitive than others (i.e., they set lower thresholds for a positive antibody result) than others. I believe most of the currently available antibody tests are still considered experimental, and they give qualitative, rather than quantitative results. This at least holds true for people who have acquired immunity (those who were exposed and recovered from Covid-19 naturally). I don't know if antibody tests given after vaccination are conducted or reported in the same way with the same parameters. The bottom line is, at this point in time, no one can tell anyone exactly how long natural (acquired through exposure and recovery) immunity lasts vs vaccine-induced immunity. It's all speculation, and "expert" opinions seem to change every day. The studies so far have conflicting results. Until well-designed, peer-reviewed and non-biased, long-term studies are conducted, right now it all depends on who you believe.