It was recommended that I take a secretory IgA test to identify potential food intolerances. Does anyone know anything about how accurate these tests are? As well as actually, how they work? Thanks in advance! PM
Hi Primal Mama,
A secretory IgA test is similar to a home pregnancy test. It uses antibodies to bind to and detect the proteins thought to provoke your food allergy/intolerance.
To diagnose a food allergy, one shouldn't begin with antibody tests because they will miss many cases, that is have many false negatives. Good clinical practice dictates beginning with a more sensitive test. Here, the gold standard is a double-blind taste test where the physician gives you the offending food but you don't know it. Once you've identified the offending food, you can use the subtler antibody test to find the offending macromolecule.
For edification, this study compares two commercial sIgA tests and show they have low sensitivity (miss many cases) but high specificity (won't tell you you're ill when you're not). When considering how to diagnose something it's important to consider the sensitivity and specificity of the tests to order the fewest number of tests required to establish the diagnosis beyond a reasonably doubt.
BTW Another name for antibody is immunoglobulin or Ig- hence IgA. So, yes, this test uses an antibody to bind an antibody. :-) There also exist IgG, IgM, IgE, IgD all of which do different things in your immune system.
I hope this helps, Mike