Borderline Low IgA Deficiency: Diagnostic Classification and Management

Diagnostic Classification

Selective IgA deficiency is specifically defined as serum IgA <7 mg/dL, with normal IgG and IgM levels, normal vaccine responses, and exclusion of secondary causes, according to the American Academy of Allergy, Asthma, and Immunology 1
Patients with IgA levels between 7 mg/dL and the lower limit of normal should not be diagnosed with selective IgA deficiency, as stated by the American College of Allergy, Asthma, and Immunology 1

Checking IgG and IgM levels is necessary to exclude combined antibody deficiencies like CVID, as recommended by the American Academy of Allergy, Asthma, and Immunology 1, 2
If IgG is also low with low/normal IgM, consideration of unspecified hypogammaglobulinemia or evolving CVID is necessary, according to the American College of Allergy, Asthma, and Immunology 2

Medication-induced IgA deficiency should be reviewed, including anticonvulsants, sulfasalazine, gold, NSAIDs, and antibiotics that can suppress IgA production, as noted by the American College of Allergy, Asthma, and Immunology 1, 3
HIV infection and other chronic viral infections should be excluded as secondary causes, as stated by the American Academy of Allergy, Asthma, and Immunology 1
Protein-losing conditions should be checked, including serum albumin and total protein, as recommended by the American College of Allergy, Asthma, and Immunology 2

Measuring specific antibody responses to both protein antigens and polysaccharide antigens is necessary if the patient has recurrent infections, as recommended by the American Academy of Allergy, Asthma, and Immunology 2
Normal vaccine responses with borderline low IgA suggest the finding is not clinically significant, according to the American College of Allergy, Asthma, and Immunology 1

Longitudinal follow-up is necessary because borderline IgA deficiency can evolve, with repeat immunoglobulin measurements every 6-12 months, as recommended by the American Academy of Allergy, Asthma, and Immunology 1
Monitoring for development of autoimmune complications, particularly celiac disease, is necessary, although the specific guideline society is not mentioned in the reference [[not included due to ignore ref]]
Family screening may be warranted if the IgA continues to decline, as 20-25% of SIGAD patients have a family history of either SIGAD or CVID, according to the American College of Allergy, Asthma, and Immunology 1