What does it mean when a lab test for strep pneumoniae igg 23 serotypes comes back as all 23 serotypes being low?

Unusual: That seems unusual to have all of them come back as "low". Even without being immunized, you certainly should have been exposed to some of these capsule serotypes over your 31 years. But...Why were you tested at all? Is there a concern about a humoral immune defect? Are you asplenic?

Further evaluation: If you have been vaccinated or have a history of recurrent sinus or respiratory infections, this response is unusual. I would consider an immune evaluation to make sure there is no other reason for this response (ie antibody or other immunodeficiency). I would also consider a Pneumovax vaccination to help boost your immune response if you are having recurrent infections. Discuss with your doc.