The difference also is that IgG testing only can check for foods a person
has consumed. If you ask someone who has consumed tomato and has a IgG
response to tomato, but has not consumed squash, and if you ask them to
consume squash, you would have to repeat the IgG test for squash. IgG
testing only is sensitive and specific for foods that you have consumed in
the past 2 weeks. While I agree with you that the two tests are not the
same, there are some inherent problems with IgG serum testing.