Lower pneumococcal IgG levels and respiratory hospitalisation in children with Down syndrome; an exploratory study

Children with Down syndrome (DS) are at increased risk for recurrent and severe respiratory infections. Pneumococcal IgG measurements are used in clinical practice to evaluate humoral immunity, yet their clinical relevance in DS remains unclear. We examined potential associations between pneumococcal IgG concentrations and clinical characteristics in children with DS, including recurrent infections and respiratory hospital admission. We conducted a retrospective study in a paediatric DS cohort with repeated pneumococcal IgG measurements obtained from left-over plasma samples using ELISA and multiplex bead-based (Luminex) assays. Potential associations with selected clinical variables, including respiratory hospital admission, the presence of autoimmune comorbidity, and infections, were assessed using mixed-effects modelling. A cross-sectional analysis using only the last available measurement per participant was performed to address the temporal uncertainty between the static information on the clinical variables and the repeated antibody measurements. Across both assays, a history of hospital admission for respiratory problems was associated with lower pneumococcal IgG concentrations in linear mixed-effect regression analyses; a history of autoimmune comorbidity was associated with higher concentrations. A history of recurrent ear infection was associated with lower ELISA-measured IgG concentrations in the last-timepoint analysis. Conclusion: Our exploratory analysis suggests a potential association between lower pneumococcal IgG concentration and selected clinical characteristics in children with DS. These findings support further investigation into the clinical relevance of pneumococcal antibody measurements in children with DS in larger, prospective studies.