How exhaustive (especially considering cost) should an immunological workup be for patients with extensive, recurrent, or deep seated Staph aureus infections without obvious immunocompromise (e.g. cancer, diabetes, steroids) or recurrent breaks in skin integrity?

Obviously, children with recurrent Staph aureus infections should be evaluated for both CGD (chronic granulomatous disease) and IgM deficiency. However, the majority of adults with recurrent SA infections do not have a known systemic immunodeficiency. We should keep in mind that Staph aureus is an a...