Secretory IgA and butyrate depletion in Southeast Chinese infants with cow's milk allergy: pathogenic link and diagnostic biomarker.

OBJECTIVES: To investigate the clinical significance of fecal butyrate and SIgA as non-invasive biomarkers for CMPA diagnosis. METHODS: 45 OFC-confirmed CMPA infants (0-24 months) and 45 healthy controls were enrolled. Fecal SIgA (ELISA/BCA) and butyrate (HPLC) were quantified. Analyses included: univariate and multivariable logistic regression (adjusting for age/weight/length), symptom correlation (Cow's Milk-related Symptom Score, CoMiSS), and ROC-based diagnostic validation. RESULTS: CMPA infants showed lower SIgA (6.39 ± 2.79 vs. 11.31 ± 3.32 μg/mg; p<0.001) and butyrate (298.81 vs. 810.07 μg/g; p=0.009). Both were associated with CMPA risk and inversely correlated with symptom severity. SIgA combined with CoMiSS achieved superior diagnostic accuracy (AUC=0.909) vs. CoMiSS alone (ΔAUC=0.103, p=0.010). Butyrate with CoMiSS showed no significant improvement (ΔAUC=0.002, p=0.767). CONCLUSIONS: This study indicates that low fecal SIgA and butyrate are associated with CMPA, suggesting they may play a role in the disease. The SIgA-CoMiSS integrated workflow allows non-invasive diagnosis with improved accuracy, addressing some limitations of current OFC-based protocols.