Nearly 10% of patients with adult-onset diabetes were found to have diabetes-associated autoantibodies….
Many of those with autoimmune diabetes did not require insulin at diagnosis and, although they tended to be younger and leaner, overall did not show categorically distinct clinical differences from autoantibody-negative patients with type 2 diabetes.
Mohammed I. Hawa, PhD, from the Blizard Institute, Queen Mary University of London, United Kingdom, and colleagues write, "Only with screening for autoantibodies, especially [glutamic acid decarboxylase autoantibodies (GADA)], can they be identified with certainty."
The 6,156 study patients were aged 30 to 70 years (mean, 54.4 years) with less than 5 years (mean, 2.2 years) since diabetes diagnosis. Most (84.6%) were white, and 58.5% were men. The patients were recruited between 2004 and 2007 from 9 European countries at primary care, community, or hospital centers participating in the Action Latent Auto-Immune Diabetes in Adults (LADA) study.
At least a single type of diabetes-associated autoantibody was found in 9.7% of the total group. These included GADA in 8.8%, insulinoma-associated antigen-2 autoantibodies in 2.3%, and zinc-transporter 8 autoantibodies in 1.8%.
Of the 598 patients with autoantibodies, nearly a quarter (24.1%) had more than a single different autoantibody type and 90.5% were positive for GADA.
"These observations show that adult-onset autoimmune diabetes is not rare," the authors note.
"Clinically, knowledge that adult-onset diabetic patients have GADA should alert physicians to the increased likelihood of more rapid progression to insulin therapy," they add.
Compared with patients with autoantibody-negative diabetes, those with autoantibodies were significantly younger (49.6 vs 54.9 years; P < .001) and had significantly lower body mass indexes (27.2 vs 30.9 kg/m 2; P < .001). They also had lower systolic blood pressure and triglyceride levels and higher levels of high-density lipoprotein cholesterol (all P < .001), but low-density lipoprotein cholesterol values were not different between the 2 groups.
At the time of the study, 49.5% of autoantibody-positive patients were using insulin compared with 13.2% of the autoantibody-negative patients (P < .001).
Of the 279 autoantibody-positive patients receiving insulin, precise information on time to insulin therapy was available for 203 patients. Of those 203 patients, 56.2% were designated as having type 1 diabetes, defined by autoantibody positivity and by having started on insulin at the time of diagnosis.
Another 32.0% were classified as having LADA, defined as being autoantibody-positive but not using insulin for at least 6 months after diagnosis. A third group, accounting for the other 11.8%, fell in between: they were autoantibody-positive and started insulin more than 1 month but less than 6 months after diagnosis.
Compared with the LADA group, those with classic type 1 diabetes were younger and had lower age of onset, body mass index, waist circumference, and waist to hip ratio (P < .001 for all).
In the entire study population, the prevalence of LADA was more than 3 times greater than that of classic autoimmune type 1 diabetes (377 vs 114 patients), with an odds ratio of 3.3.
Additional analyses showed that although patients with higher titers of GADA more closely resembled patients with type 1 diabetes (younger, leaner, receiving insulin, etc) than did those with lower GADA levels, "each form of autoimmune diabetes could be found across the range of GADA titers," Dr. Hawa and colleagues note.
Diabetes Care. Published online December 17, 2012. Abstract