Evaluation of methods for proinsulin quantification and the proinsulin:C-peptide ratio in type 1 diabetes prediction

Sammanfattning

Identifying biomarkers to track disease progression in type 1 diabetes (T1D) remains a challenge. During T1D progression, β-cell stress disrupts the normal cleavage of proinsulin into insulin and C-peptide. As a result, the proinsulin to C-peptide (PI:C) ratio may reflect β-cell dysfunction and serve as a potential biomarker for disease progression. This study aimed to evaluate two methods for proinsulin quantification, enzyme-linked immunosorbent assay (ELISA) and electrochemiluminescence (ECL), for use in calculating the PI:C ratio and to assess the possibility of using this ratio for monitoring T1D progression. Proinsulin was quantified using the Mercodia ELISA and Meso Scale Diagnostics ECL assay. Both methods showed acceptable intra-assay variation (CV < 10%). ECL demonstrated better inter-assay precision (CV = 10.1%) than ELISA (CV = 15.4%) and showed superior performance in detecting low proinsulin concentrations, with no values below the detection range compared to 22% for ELISA. The evaluation of methods resulted in us proceeding with the ECL as proinsulin quantification method, mainly based on its performance in detecting lower proinsulin concentrations compared to the ELISA. A total of n = 164 serum samples from n = 41 children with multiple islet autoantibodies in the DiAPREVIT study were used for proinsulin quantification. PI:C ratios were calculated using preanalyzed C-peptide values. Children who developed T1D showed a significantly greater increase in PI:C ratio compared to those who did not, both during the first two years of follow-up (p = 0.004) and in the two years preceding T1D diagnosis (p < 0.001). The increase in PI:C ratio close to diabetes debut in the children developing T1D revealed by this study indicates that PI:C ratio possibly could be used as a biomarker for β-cell dysfunction and T1D progression in the future.