Frequency and risk factors of low immunoglobulin levels in patients with inflammatory bowel disease

Inflammatory bowel diseases (IBD) are considered to be dysregulated, immune-mediated disorders; and immunosuppressive medications are the mainstay of their treatment. Clinically, we have often observed low serum immunoglobulin (Ig) levels in these patients. The aim of this study was to assess the frequency and risk factors of secondary humoral immunodeficiency in IBD patients.

We conducted a cross-sectional study of eligible IBD patients with Crohn's disease (CD), ulcerative colitis (UC), indeterminate colitis (IC) or restorative proctocolectomy with ileal pouch, who having serum Ig measured. Demographic and clinical variables were measured. Univariate and multivariate analyses were performed.

A total of 324 patients was included, with a mean age of 38.8 years and 158 (48.8%) being male. Low IgG, IgG1, IgA, and IgM were found in 22.7%, 23.4%, 7.9%, and 10.9% of patients, respectively. The shared risk factors for a low IgG or IgM level were increasing age [odds ratio (OR) = 1.13; 95% confidence interval (CI) 1.03-1.23 for low IgG level and OR = 1.33; 95% CI 1.15-1.56 for low IgM level] and hypoalbuminemia (OR = 1.83; 95% CI 1.01-3.33 for low IgG level and OR = 3.17; 95% CI 1.23-8.15 for low IgM level). In addition, thioprine use was associated with low IgA level (OR = 2.76; 95% CI 1.03-7.39). IBD disease duration was a risk factor for low IgG1 level (OR = 1.40; 95% CI 1.12-1.76). The presence of concurrent primary sclerosing cholangitis (OR = 0.064; 95% CI 0.007-0.60) and the use of biologics (OR = 0.16; 95% CI 0.033-0.79) were associated with normal IgG1 level. IgG level was lower in CD patients than that in UC/IC and ileal pouch patients (P = 0.042). IgG and IgA levels were elevated in patients with inflammatory conditions of the pouch (P = 0.01; P = 0.003, respectively).

Low Ig level appears to be common in IBD patients. Increasing age, disease duration and hypoalbuminemia appeared to be risk factors. The findings may provide rationale for targeted therapy to boost humoral immunity in selected patients with IBD.