“You can have a patient that has normal immunoglobulins and abnormal responses to protein antigens as well. Historically, I’ve seen these patients. They do happen. They are out there.”

– Dr. Benjamin Prince

Specific antibody deficiency (SAD) has never been a clean diagnosis. Some patients carry normal immunoglobulins and still land in clinic with recurrent infections and poor vaccine responses. The newer pneumococcal vaccines have scrambled the old testing pathways. This episode covers which parts of the workup still hold up, and where a titre should actually change what you do next.

Our host is joined by Dr. Benjamin Prince, Associate Professor of Pediatrics and Associate Division Chief of Research in Allergy and Immunology at Nationwide Children’s Hospital in Columbus, Ohio. He walks through the shifting definition of SAD, what pneumococcal titres can and can’t tell you, and how to read testing in the Prevnar 20 era.

On this episode, they discuss:

• Clinical history as the gatekeeper for who gets worked up
• What Prevnar 20 did to polysaccharide response testing
• Reading the patient ahead of the titre
• Recommendation 4.7 and impaired protein-antigen responses
• Pneumococcal titre thresholds: useful, imperfect, lab-dependent
• The management range, from watchful waiting through immunoglobulin replacement

A useful listen for any clinician who has stared at a borderline pneumococcal panel and wondered whether to keep pulling the thread. The lab pathway exists, but the history is still what tells you whether the result will mean anything.

Posted on June 23, 2026.