Clinical and immunologic features of adult primary antibody deficiency according to IVIGRT exposure

Primary antibody deficiency (PAD) in adults is increasingly recognized, but remains underdiagnosed and undertreated. We described the clinical and immunologic features of adult patients with PAD according to real-world exposure to intravenous immunoglobulin replacement therapy (IVIGRT) and explored whether the Ajou-PAD score reflects treatment decisions in routine clinical practice.

We conducted a retrospective cohort study at Ajou University Hospital (January 1, 2020-November 18, 2024), screening adults (age ≥ 18 yr) diagnosed with PAD, and excluding those with IVIGRT exposure before diagnosis. After 1:1 propensity score matching by age and sex, clinical and laboratory findings between the IVIGRT-exposed and -unexposed groups were compared. The discriminatory performance of the Ajou-PAD score, a composite index integrating clinical and immunologic parameters, was evaluated for IVIGRT exposure using receiver operating characteristic analysis.

The final matched cohort included 602 patients (301 per group). Immunoglobulin G subclass 3 deficiency (IgG3SCD) was the most prevalent phenotype and more frequent in the IVIGRT-exposed group than in the IVIGRT-unexposed group. The Ajou-PAD score showed modest discriminatory performance for IVIGRT exposure (AUC = 0.61; 95% CI, 0.56-0.65).

In Korean adults with PAD, IgG3SCD was the most prevalent phenotype and was more common among patients receiving IVIGRT in routine clinical practice. The Ajou-PAD score showed modest discriminatory performance for IVIGRT exposure and should be considered an exploratory adjunct rather than a standalone tool for treatment decision-making.