A new ELISA for autoantibodies to steroid 21-hydroxylase

A new ELISA for autoantibodies to steroid 21-hydroxylase (21-OH Ab) is described.

In the assay test sample autoantibodies form a bridge between 21-OH coated onto the plate well and liquid phase 21-OH-biotin. Bound 21-OH-biotin is detected by the addition of streptavidin peroxidase and colorogenic peroxidase substrate.

Of 100 samples from patients with autoimmune Addison's disease, 86 (86%) were positive for 21-OH Ab ELISA whereas 84 (84%) were positive in an immunoprecipitation assay based on 125I-labeled 21-OH. Six (0.6%) of 928 healthy adult blood donors and 1 (2.0%) of 49 adult patients with type 1 diabetes mellitus (T1DM) were positive by ELISA. No samples from adult patients with Graves' disease (GD; n=50), celiac disease (n=29), systemic lupus erythematosis (n=9) or rheumatoid arthritis (n=20) were positive by ELISA. However, 2/51 (3.9%) children with GD, 3/69 (4.3%) children with Hashimoto's thyroiditis (HT) and 3/119 (2.5%) children with T1DM alone or associated with autoimmune thyroid disorders were ELISA positive.

The new assay should be useful for screening patients known to be at increased risk of developing clinical autoimmune Addison's disease, in particular children with HT, GD and/or T1DM.