Glutamic Acid Decarboxylase and Islet Cell Cytoplasmic Autoantibodies Positivity in Latent Autoimmune Diabetes of Adults: Need for Early Insulinisation

Introduction: Latent Autoimmune Diabetes of Adults (LADA) remains a poorly understood disease at both the clinical and research level and usually misdiagnosed as Type 2 Diabetes Mellitus (T2DM) and treated with Oral Hypoglycaemic Agents (OHA). This might lead to accelerated beta-cell destruction leading to early insulin-dependency in these patients. Screening of T2DM and determination of C-peptide and insulin antibodies helps to differentiate this disease from LADA. Early insulinisation of these patients prevents beta-cell destruction and preserves residual beta-cell function. Aim: To screen type 2 diabetic patients for potential LADA subjects based on LADA clinical risk score and to confirm them as LADA based on Glutamic Acid Decarboxylase (GADA) positivity and Islet Cell Cytoplasmic Autoantibodies (ICA) positivity. Materials and Methods: The hospital based cross-sectional study was done on 945 T2DM patients attending Out Patient Department (OPD) of Rajarajeswari Medical College and Hospital, Bengaluru, Karnataka, India from March 2017 to May 2019. Patients were screened using LADA clinical risk score and potential LADA subjects were identified and tested for C-peptide, GAD and IC Antibodies to confirm LADA. C-Peptide and GAD antibodies were measured by ELISA method. IC antibodies were observed using immunoflorescence microscopy. Inferential Statistics (Chi-square test, Z test, t-test) by using SPSS V20 and MS Excel was used. Results: Out of 945 T2DM patients, 188 patients (20%) were considered as potential LADA subjects based on LADA clinical risk score. All 188 subjects were tested for C-peptide, GAD and IC antibodies. 36% (68 subjects) of them had low C-peptide levels. Among them four subjects (6%) had high GADA titer confirming them as LADA subjects. Three (4%) of the subjects had low GADA titer, remaining 61 subjects did not show antibody positivity. Only one of them had both IC antibody positivity out of four subjects with high GADA titer. Remaining 64% (120 subjects) had normal C-peptide levels and antibody negative. Conclusion: Using 5-point LADA clinical risk score 20% were identified as potential LADA subjects out of 945 T2DM subjects. 6% of the potential LADA subjects had high GADA titer confirming them as LADA, who may be benefited by early insulinisation.