Antibody deficiencies and complement deficiencies are the most frequent primary immunodeficiencies (PIDs) in adults and are mainly revealed by recurrent and/or severe bacterial infections. The objective of this study is to evaluate a systematic research strategy of PIDs in adults with unexplained bacterial infections.
A regional prospective study was conducting in 15 centers (NCT02972281). Main inclusion criteria were recurrent benign bacterial respiratory tract infections (RTIs) (group 1), severe bacterial RTIs requiring hospitalization (group 2), and/or invasive infections documented with encapsulated bacteria (group 3). Main exclusion criteria were all local (including tobacco use) and general associated conditions which could explain infections. If required to confirm or assess an antibody deficiency, response to polysaccharide antigens was assessed by serotype-specific ELISA (7-16 serotypes) after PPV23.
From March 2015 to April 2019, 96 patients were included (33 males, median age 54 years), and full data were available in n=78 at the time of the analysis. Thirty-two antibody deficiencies were diagnosed, giving an estimated frequency between 33.3% (n=32/96) to 41% (n=32/78). Specific Polysaccharide Antibody Deficiency (SPAD) was the most frequent diagnosis by far (n=28/32), and was made in 14, 7 and 7 patients from groups 1 to 3, respectively. Outcome after diagnosis was available in n=25. Depending on infectious history, SPAD patients received antibiotic prophylaxis (azithromycin) (N=4) and/or immunoglobulins replacement therapy (N=6), the latter being dramatically efficient in all cases.
After having ruled out other PIDs, SPAD should be screened in patients with unexplained recurrent and/or severe bacterial infections.