Endocrine Abstracts

Introduction: Almost all type 1 diabetes mellitus (T1DM) patients have autoantibodies (ab) at disease onset. These ab prevalence varies according to patients’ age, origin and disease duration.

Aim: Determine diabetes mellitus ab prevalence in a paediatric and adult T1DM Portuguese according to their age on diagnosis, gender and diabetes duration.

Methods: Retrospective review of T1DM ab (glutamic acid decarboxylase 65 autoantibodies – GAD, islet cell autoantibodies – ICA, insulin autoantibodies - IAA, tyrosine phosphatase–like insulinoma antigen-2 antibodies - IA2) evaluated from 2018 to 2021. Considering the age at ab assessment, patients were divided into prepuberty (0–12 years) or postpuberty (≥ 13 years) and further subdivided into G1 and G2 when the assessment was at diagnosis or during follow-up, respectively.

Results: Included 156 patients (56.4% men; mean age 21.9±15.5 years). Of these, 101 (64.7%) belonged to G1 and 55 (35.3%) to G2 (mean age at diagnosis 15.1±10 vs. 20.7±12.1 years;P=0.004). In G1, 65 (64.4%) were men and 45 (44.6%) were prepubertal. In G2, 23 (41.8%) were men and T1DM mean duration was 13.4±14.2 years. The overall prevalence of positive ab was 83.2% in G1 and 69.1% in G2 (P=0.042), without differences between genders. There was a higher prevalence of GAD (P=0.23), IA (P=0.009) and ICA (P=0.006) in G1 and IAA (P=0.17) in G2. In G1, the mean number of positive ab was 1.6 and in G2 was 1.1 (P=0.017). In prepubertal G1 patients, positive ab prevalence was 88.9% (highest rate between 6–12 years) and in postpubertal was 78.6%, without significant difference regarding each ab prevalence in pre or postpuberty. In G2, patients diagnosed in postpuberty had a higher prevalence of ab, with a significant difference for GAD (P=0.011) and ICA (P=0.025). Patients with all ab negative (30.9%) had a T1DM duration of 19.2±13.1 years, while patients with at least 1 positive ab (69.1%) had T1DM duration of 10.7±14 years (P=0.039). Spearman’s correlation test indicated that there was a negative and moderate correlation between the number of positive ab and the diabetes duration (rs=-0.5, P=0.001).

Conclsions: In our cohort, more than 80% of T1DM patients had positive ab at diagnosis. GAD and IA were the most prevalent ab, contributing to T1DM diagnosis both in pre and postpubertal patients. There was no difference between genders and ab prevalence. The number of positive ab decreased with disease duration.