Prevalence and clinical characteristics of insulin-treated, anti-GAD-positive, type 2 diabetic subjects in an outpatient clinical department of a Dutch teaching hospital.

Abstract

BACKGROUND: In clinical practice, type 1 and type 2 diabetic patients are sometimes difficult to distinguish. Type 1 diabetes has an immune-mediated pathogenesis, resulting in a loss of insulin-secreting beta-cells. Type 2 diabetes mellitus is characterised by a relative insulin insufficiency, without the presence of an autoimmune aetiology, initially due to insulin resistance and later also accompanied by defective insulin release. Latent autoimmune diabetes of the adult (LADA) is a subgroup of diabetes, somewhere on the borderland between type 1 and type 2 diabetes. LADA is characterised by a late-age onset and relatively mild progression, but with unmistakable signs of autoimmunity, such as the presence of the autoimmune antibodies anti-GAD65, anti-insulin antibodies, or anti-Ia-2ab. OBJECTIVE: To establish the prevalence of anti-GAD ina diabetic outpatient clinic of a Dutch, non-university,teaching hospital and to describe these patients clinical and laboratory features, especially of the metabolic syndrome. METHODS: We evaluated GAD65 antibodies and other parameters in 244 selected diabetic patients, who had been on oral therapy for at least three months before becoming insulin-dependent. RESULTS: Twenty-six patients (11.6%) were positive for GAD65 antibodies. These patients had a significantly lower BMI (27.8 +/- 4.5 vs 31.1 +/- 4.9; p<0.01); less often cerebrovascular accidents (19.2 vs 34.9%; p<0.01) and a higher HDL cholesterol (1.73 +/- 0.53 vs 1.21 +/- 0.38; p<0.05). In contrast, anti-GAD patients had a significantly higher prevalence of hypothyroidism (23.0 vs 6.6%; p<0.05). CONCLUSION: Anti-GAD-positive patients represent a sizable proportion of type 2 diabetes in a second-line outpatient clinic, and they are characterised by lower parameters of the metabolic syndrome, but higher prevalence of other autoimmune phenomena such as hypothyroidism.