Endocrine Abstracts

Introduction: Latent Autoimmune Diabetes of Adult (LADA) is a form of adult onset type1diabetes. It usually presents after age 30 years and has many demonstrable antibodies, Glutamic Acid Decarboxylase (GAD) being one of them. Detection of LADA has definite prognostic and treatment implications as 10% of adults with diabetes in UKPDS had LADA and majority of them required insulin within 6 years of diagnosis. Screening by using GAD antibody has been said to be a superior method as no clinical feature reliably discriminates LADA from type 2 diabetes. However, recent reports (Fourlanos S et al. Diabetes Care 2006), suggest that presence of at least two distinguishing clinical features for diagnosing LADA (age <50, acute osmotic symptoms, BMI <25, personal or family history of auto-immune disease) can detect two-thirds of adults with LADA and has 90% sensitivity.

Aims: The aim was to try and identify from the history, the reasons for requesting GAD antibody testing, and whether these requests were appropriate on the above-mentioned clinical grounds.

Methods: We looked at the computer records and history of all patients who had GAD measurements undertaken in our hospital over the last 2 years.

Results: Out of a total of 18 patients who had GAD measurements, 12 had diabetes and 6 had other neurological/medical problems. Among diabetics, the presumed diagnoses were: type 1–4, type 2–3, gestational-1 and unspecified-4. The various reasons for GAD antibody requests were: query about diabetes type (1 or 2), persistent weight loss, increase in insulin requirements, positive family history of diabetes and associated multi-endocrine involvement. Age, BMI or symptoms were not taken into account. GAD antibodies were negative in all 18 patients.

Conclusion: It is not surprising that GAD antibody testing in our hospital was negative (especially in the diabetic patients) given the inappropriate nature of requests, at least based on the chosen clinical criteria. GAD antibody testing should only be performed in those with strong clinical suspicion of LADA. In such patients, GAD measurements can be helpful in further confirming or refuting the diagnosis as clinical features alone cannot be relied upon in all cases of LADA. We will be looking to re-audit our use of GAD antibody testing in light of these findings. Simple clinical features as suggested in the above study should help streamline GAD antibody testing and hopefully yield positive results if requested in appropriate patients.