Serum immunoglobulin A in pediatric appendicitis.

The pathogenesis of appendicitis is not fully understood. This study aimed to evaluate the associations between serum IgA and pediatric appendicitis. A prospective cohort study in which children ≤ 15 years with suspected appendicitis were enrolled at the Pediatric Emergency Department during 2017–2021. Blood samples were analyzed for serum IgA concentrations. Primary outcomes were appendicitis and complicated appendicitis. Associations were evaluated using univariate and multivariable logistic regression. Primary exposure was serum IgA concentrations, both in absolute concentrations as well as categorized as either normal, high or low in relation to age-dependent reference intervals. Independent variables were age, sex, symptom duration and/or presence of appendicolith. 177 children were included. Median age was 10 (IQR 8–12) years and 102 (58%) were boys. 137 (77%) had appendicitis, of which 58 (42%) were complicated. Median serum IgA among the children with appendicitis was 1.10 (IQR 0.68–1.52) g/L, compared to 1.11 (IQR 0.78–1.61) g/L in the non-appendicitis group, p = 0.44. Among the children with uncomplicated appendicitis, median IgA was 1.18 (0.80–1.58) g/L, compared to 0.92 (0.59–1.48) g/L among the children with complicated appendicitis, p = 0.07). Serum IgA was neither significantly associated with appendicitis (cOR 0.72 [95% CI 0.45–1.16], p = 0.18; aOR 0.70 [95% CI 0.41–1.20], p = 0.20) nor complicated appendicitis (cOR 0.71 [95% CI 0.41–1.21], p = 0.20); aOR 0.79 [95% CI 0.42–1.50], p = 0.47). Analyses of high and low serum IgA according to age-dependent reference intervals did not show any significant associations to appendicitis or complicated appendicitis, neither in the univariate nor the multivariable analyses. There were no significant associations between serum IgA and odds of appendicitis or complicated appendicitis in children. This does not rule out associations between appendicitis and secretory IgA found in the appendix mucosa or lumen. This should be the target for future studies on IgA and appendicitis.