Specific Antibody Deficiency.

What is Specific Antibody Deficiency?

A normal immunoglobulin panel does not necessarily mean the immune system is working properly. Some patients produce adequate total antibody but fail to mount effective antibody responses to specific bacteria — particularly Streptococcus pneumoniae, Haemophilus influenzae, and other encapsulated organisms. The result is a pattern of recurrent sinus, ear, and respiratory infections that look like ordinary infections but keep coming back.

Specific Antibody Deficiency is frequently missed because routine bloodwork shows normal IgG and IgM. Identifying it requires specifically testing the immune response to vaccination — measuring antibody levels before and after a polysaccharide vaccine to see whether the body can mount a protective response.

When to consider evaluation

• Recurrent sinus or respiratory infections despite normal IgG
• Persistent or chronic bronchitis requiring repeated antibiotic courses
• Failure to respond adequately to vaccination
• Bronchiectasis identified on imaging without other identified cause
• Chronic productive cough

How it is diagnosed

Diagnosis requires vaccine response testing. The standard approach measures pre-vaccination pneumococcal antibody titers, administers an unconjugated pneumococcal polysaccharide vaccine, and re-measures titers four to eight weeks later. The pattern of response — how many serotypes the patient responds to, and the magnitude of the response — determines the diagnosis.

A complete workup typically also includes IgG subclasses, lymphocyte subset analysis, and assessment for any contributing structural disease such as chronic sinusitis or bronchiectasis.

Treatment options

Treatment depends on severity and individual circumstances. Many patients with mild Specific Antibody Deficiency are managed conservatively — with prompt treatment of infections as they occur and aggressive management of contributing factors. Some patients benefit from prophylactic antibiotics during high-risk seasons.

Patients with severe or refractory Specific Antibody Deficiency may be candidates for immunoglobulin replacement therapy. The decision is individualized and made together — taking into account infection burden, quality of life impact, and patient preference.

What to expect at your visit

A first visit typically includes a thorough infection history, review of any prior labs, and discussion of the testing plan. Vaccine response testing is performed in stages — baseline labs, vaccination, and follow-up labs — so the diagnostic process takes a few weeks. Dr. McNeil reviews each result personally and discusses findings and treatment options at follow-up.