Long-term follow-up of organ-specific antibodies and related organ dysfunction in type I diabetes mellitus

Objective: Diabetes mellitus type I (DM1) is associated with other autoimmune disorders. To our knowledge, there are no longitudinal data considering the long-term clinical relevance of organ-specific antibodies (OS -Ab) in DM1 patients. We performed a long-term retrospective longitudinal study in order to investigate the presence and diagnostic accuracy (positive predictive value: PPV and negative predictive value: NPV) of OS -Ab in DM1 patients. Research design and methods: In a retrospective longitudinal study, the presence of OS -Ab and related organ function were analysed in 396 DM1 patients (184 F/212 M, age 44±13 years, age at onset of DM1 21±13 years), with a median follow-up time of 23±10 years. Results: OS -Ab frequencies at baseline were: antibodies against thyroglobulin (Tg-Ab) 4.3%, antibodies against thyroid peroxidase (TPO -Ab) 8.1%, Tg- and/or TPO -Ab 10.4%, antibodies against parietal cells (PCA) 5.8% and antibodies against adrenal cortex (ACA) 0.5%. The occurrence of (sub)clinical hypothyroidism was higher in patients with Tg-Ab (47%) or TPO -Ab (42%) than in those without these antibodies (6.2 and 5.1%, respectively, p<0.001). PPV and NPV for Tg-Ab were 0.60 and 0.88, respectively, for TPO -Ab 0.54 and 0.91. Also in patients with PCA, organ dysfunction occurred more often (61%) than in patients without PCA (9.7%, p<0.001). PPV for PCA was 0.61 and NPV 0.90. NPV and PPV for ACA could not be calculated because of the low prevalence. Conclusion: Long-term follow-up of 396 DM1 patients shows that the presence of thyroid antibodies and/ or parietal cell antibodies is clearly associated with dysfunction of the corresponding organ.