My results show low igg but normal level igg subclasses, is the low igg level still significant?

Don't know: Need to know why the tests were ordered in the first place. If you suffer from recurrent or chronic sinus or lung infections, then even a normal total IgG may not be enough since it is whether your body can produce specific defense against bacterial (qualitative) than the total number (quantitative) that matters most. See an allergist.