Impact of Sample Type on ADAP-Based Autoantibody Detection for Type 1 Diabetes Population Screening

<b><i>Context:</i></b> The growing worldwide interest in early-stage type 1 diabetes (T1D) screening highlights the need for efficient and affordable approaches. Advanced analytical technologies such as Antibody Detection by Agglutination-PCR (ADAP) have improved large-scale sample handling, but optimal sample selection for simplified collection and processing remains a major challenge in screening designs. <b><i>Objective:</i></b> To assess ADAP for T1D-related autoantibody detection in different blood-derived samples to select the optimal sample type for large-scale screening. <b><i>Methods:</i></b> Autoantibodies against insulin (IAA), glutamate decarboxylase (GADA), protein tyrosine phosphatase IA-2 (IA2A), and zinc transporter 8 (ZnT8A) were analyzed by ADAP in 171 patients with stage 3 T1D (13.7 years; interquartile range [IQR]: 6.5-15.0) and 95 healthy controls (41.9 years; IQR: 29.5-56.7) previously studied by radiobinding assay (RBA). Comparison of sensitivity/specificity of ADAP and RBA in serum was assessed, as well as ADAP concordance across serum, plasma, EDTA-anticoagulated whole blood, and dried blood spot (DBS). Whole-blood stability was also investigated. <b><i>Results:</i></b> ADAP-based detection of two or more autoantibodies in serum demonstrated high sensitivity (87.1%) and specificity (100%), with strong concordance with RBA (Cohen's kappa 0.90). Autoantibody analysis in whole blood by ADAP showed high agreement with serum, making it a consistent alternative. In contrast, DBS sampling had reduced concordance, which led to fewer positive detections and suggests a potential bias for T1D screening. A remarkable advantage was that autoantibodies in unrefrigerated whole blood remained stable for up to 7 days (IAA) and 20 days (GADA, IA2A, and ZnT8A), and also after four freeze-thaw cycles, considerably simplifying logistics. <b><i>Conclusion:</i></b> Pancreatic autoantibody detection in whole blood with ADAP provides a stable and more efficient diagnostic solution for T1D population screening, with simplified preparation, low-volume requirements, and high diagnostic consistency comparable with serum-based assays.