Combining antibody with T-cell assays boosts type 1 diabetes diagnosis

Combining enzyme-linked immunospot assays and antibody detection seems to improve the diagnosis of type 1 diabetes mellitus, a recent study has found.

Fifty-four patients with type 1 diabetes mellitus participated in the study. Radioligand assays were performed for the detection of antibodies against glutamic acid decarboxylase (GAD), zinc transporter 8, and islet antigen-2. On the other hand, interferon-γ-secreting T cells were measured through enzyme-linked immunospots. A parallel group of 56 healthy controls was also included.

Of the diabetic participants, 35 had at least one kind of islet antibody, the most common of which was targeted to GAD (n=35). Among controls, in comparison, only one was positive for anti-GAD antibodies.

Nineteen patients had idiopathic type 1 diabetes, of whom 11 were detected to be positive for T-cell responses in immunospot assays. Of the 35 patients with autoimmune type 1 diabetes, 19 had similar T-cell positivity for islet antigens.

Individually, the T-cell and antibody assays were statistically comparable in terms of sensitivity (55.6 percent vs 64.8 percent; p=0.33) and specificity (94.6 percent vs 98.2 percent; p=0.31). There was also no significant correlation between the two assays, as determined by Spearman analysis (coefficient, –0.03; p=0.83).

However, combining both assays led to a significant improvement in the diagnostic sensitivity of autoimmune diabetes as opposed to detecting antibodies alone (85.2 percent vs 64.8 percent; p=0.015), without sacrificing specificity (94.6 percent).

“[T]ype 1 diabetes mellitus was widely perceived as a T-cell-mediated autoimmune disease,” the researchers said. “However, the diagnosis of autoimmune diabetes is currently mainly based on islet antibodies, which are absent in idiopathic type 1 diabetes mellitus.”

“In the present study, combining T-cell assay and antibody detection can improve the diagnostic sensitivity of autoimmune diabetes,” they added.