Question: When should I decide to test for IgG, IgM, or total immunoglobulin?

Answer passage (source: CDC):
page_title: Frequently Asked Questions
section_headers: Symptoms & Testing
What is antibody testing? And can I be tested using this method?
section_content: Antibody testing checks a sample of a person’s blood to look for antibodies to
SARS-CoV-2, the virus that causes COVID-19. These antibodies are produced when
someone has been infected, so a positive result from this test indicates that
person was previously infected with the virus.
CDC is working with other federal agencies to evaluate the performance of
commercially manufactured antibody tests that are becoming increasingly
available from healthcare providers. This evaluation is expected to be
completed in early May.
We do not know yet if the antibodies that result from infection with SARS-
CoV-2 can protect someone from reinfection with this virus (immunity) or how
long antibodies to the virus will protect someone. Scientists are conducting
research to answer those questions.
Antibody tests may not be able to tell you if you are currently infected
because it typically takes 1 to 3 weeks to develop antibodies to SARS-CoV-2.
To tell if you are currently infected, you would need a test that identifies
the virus in samples from your upper respiratory system, such as a
nasopharyngeal swab.

Reviewer feedback on this answer:
Discusses antibody testing, but doesn't provide guidance on choosing between the three types of test mentioned in the question.
There is a good amount of information here about the testing.   It seems helpful to someone asking these questions.

Reviewer ratings:
Could be Improved
Excellent

Answer passage (source: CDC):
page_title: Test for Current Infection
section_headers: How to decide if you should get a viral test
section_content: Not everyone needs to be tested for COVID-19. Here is some information that
might help you make decisions about getting a viral test.

Most people have mild illness and can recover at home without medical care. They may not need to be tested.
At this time, there is no treatment specifically approved for people who have COVID-19.

CDC has guidance for who
should be tested, but decisions about testing are made by state and local
health departments or healthcare providers.

Reviewer feedback on this answer:
Provides general guidance on who should get tested, but doesn't mention the three tests the question is specifically asking about.
This talks about getting testing, but there's not a lot of information.  It seems like it not very helpful.

Reviewer ratings:
Bad
Could be Improved

Answer passage (source: CDC):
page_title: Frequently Asked Questions about Laboratory Testing and COVID-19
section_headers: For All Laboratories: Serology
Should I test for IgG, IgM, or total immunoglobulin?
section_content: The decision to test for IgG, IgM, or total immunoglobulin, which could also
include IgA, depends on the purpose for testing. Testing for total
immunoglobulin may increase sensitivity for identifying people who have been
recently infected. Testing for IgG may be a better marker of durable immunity
to SARS-CoV-2. However, we need additional data on the maturation of the
immune response to SARS-CoV-2 to make evidence-based recommendations for all
testing scenarios. Scientists from CDC and elsewhere are investigating how
SARS-CoV-2 antibody responses develop over time.

Reviewer feedback on this answer:
Provides guidance for deciding between IgG, IgM or total immunoglobulin tests.
This is a direct answer.  It talks all about getting the testing done.

Reviewer ratings:
Excellent
Excellent