CVID? No. SAD? Maybe.

“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 PrinceSpecific 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.Dr. Mariam Hanna 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.Key PointsClinical history as the gatekeeper for who gets worked upWhat Prevnar 20 did to polysaccharide response testingReading the patient ahead of the titreRecommendation 4.7 and impaired protein-antigen responsesPneumococcal titre thresholds: useful, imperfect, lab-dependentThe management range, from watchful waiting through immunoglobulin replacementA 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.Have an idea for the show or a comment, send us a text!Visit the Canadian Society of Allergy and Clinical ImmunologyFind an allergist using our helpful toolFind Dr. Hanna on X, previously Twitter, @PedsAllergyDoc or CSACI @CSACI_caThe Allergist is produced for CSACI by PodCraft Productions