Diagnostic role of antibodies to glutamic acid decarboxylase in latent autoimmune diabetes mellitus in adults.

OBJECTIVE

To investigate the diagnostic role of antibodies to glutamic acid decarboxylase (GAD65-Ab) in latent autoimmune diabetes of adults (LADA) and the frequency of GAD-Ab in Chinese patients initially diagnosed as non-insulin-dependent diabetes mellitus (NIDDM).

METHODS

Forty-five control subjects and 195 consecutive inpatients initially classified as NIDDM with > or = 35 years of age at onset and nonketotic history for > 6 months after diagnosis, were recruited. In vitro transcripted and translated recombinant human 35S-GAD65 was used in radioligand assay of GAD-Ab.

RESULTS

The overall prevalence of GAD65-Ab was 14.8% (29/195) in NIDDM patients and 2.2% (1/45) in control subjects, respectively. Of the 29 GAD65-Ab positive patients, 17 (58.6%) were insulin-deficient while 12 (41.4%) were non-insulin-deficient. The prevalence of GAD65-Ab in NIDDM group with age of < 40 years at diabetes onset, ketotic history, body mass index (BMI) < 21 kg/m2, were significantly higher than that of corresponding control diabetic subgroups (2.5, 4.1 and 3.2 times, respectively). The sex, duration, symptoms of polyphagia, polydipsia, polyuria and weight loss at onset of the disease were not related to the prevalence of GAD65-Ab positivity.

CONCLUSIONS

In China, patients initially diagnosed as NIDDM may in many cases suffer from LADA. Testing by GAD65-Ab may be of assistance to identifying LADA at the earliest stage of disease.