Selective Immunoglobulin A Deficiency Among Omani Patients Screened for Celiac Disease: A Cross-sectional Study

Objectives: Selective immunoglobulin A deficiency (SIgAD) is characterized by an isolated deficiency of serum IgA while immunoglobulin G (IgG) and immunoglobulin M (IgM) levels remain normal. Symptoms range from asymptomatic to recurrent infections. We aimed to determine the prevalence of IgAD and SIgAD among Omani patients undergoing screening for celiac disease. Methods: This cross-sectional study included Omani nationals aged above one year, who were screened for celiac disease with anti-tissue transglutaminase (anti-tTG) IgA at Royal Hospital, Muscat, from January 2005 to December 2023. IgAD was defined as a total serum IgA level below the age-dependent reference range. SIgAD was diagnosed when both IgG and IgM values were within their respective reference limits. The prevalence of IgAD and SIgAD was statistically reviewed. Results: Of the 9615 individuals who underwent screening for celiac disease, 114 had low IgA levels. The prevalence of IgAD was 1.2%, and among these, 0.4% were confirmed to have SIgAD. The majority were > 14 years. Patients aged 6–14 years and > 14 years were more likely to have IgAD compared to 1–2 years old. Only 39 (34.2%) patients underwent further testing to confirm SIgAD, while the remaining 75 (65.8%) did not undergo follow-up IgG and IgM testing. Among the patients with confirmed SIgAD, 11 (28.2%) underwent further testing with anti-tTG IgG antibody, with only one (9.1%) testing positive for celiac disease as confirmed by esophagogastroduodenoscopy (EGD) and histopathology. Patients with anti-tTG IgG and EGD exhibited a significantly increased risk of low IgA levels. The remaining 28 (71.8%) patients did not undergo further celiac disease workup (anti-tTG IgG antibody, EGD, or genetic testing). Conclusions: IgAD was present in 1.2% of Omani patients evaluated for celiac disease, and 0.4% had confirmed SIgAD. Referral to an immunologist is recommended when IgG/IgM levels are low or infections are recurrent.