Anti-thyroid peroxidase antibody, IA-2 antibody, and fasting C-peptide levels predict beta cell failure in patients with latent autoimmune diabetes in adults (LADA)--a 5-year follow-up of the Ehime study.

OBJECTIVE: To clarify the natural course and factors involved in beta cell failure in Japanese latent autoimmune diabetes in adults (LADA) patients. RESEARCH DESIGN AND METHODS: Insulin secretion in 57 LADA patients identified from among 4980 adult-onset diabetic patients in a hospital-based Ehime study were examined over a 5-year period. Postprandial serum C-peptide levels below 0.33 nmol/l were defined as beta cell failure. The involvement of clinical and immunological factors in the progression to beta cell failure were evaluated.
RESULTS: Forty-two of the fifty-seven LADA patients completed the 5-year follow-up. Eleven (26.2%) required insulin treatment and five (11.9%) progressed to beta cell failure. A Cox regression analysis revealed that positive anti-thyroid peroxidase antibody (TPOAb) and insulinoma-associated protein 2 (IA-2Ab) were associated with the need for insulin treatment (p<0.05 and p<0.01, respectively). Positive TPOAb, anti-thyroglobulin antibody (TGAb), IA-2 antibody (p<0.01 for each), and lower serum fasting C-peptide levels (p<0.05) were contributors to the progression to beta cell failure. Involvement of type 1 diabetes susceptible HLA class II genes was not evident.
CONCLUSIONS: Japanese LADA patients are a heterogeneous population. In addition to IA-2 antibody, presence of TPOAb and fasting C-peptide level could indicate an oncoming deterioration of beta cell function.