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

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.

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.

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).

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.