Rapid Point-of-Care Test for Determination of C-Peptide Levels.

C-peptide is co-secreted with insulin and is not subject to hepatic clearance and thus reflects functional β-cell mass. Assessment of C-peptide levels can identify individuals at risk for or with type 1 diabetes with residual β-cell function in whom β cell-sparing interventions can be evaluated, and can aid in distinguishing type 2 diabetes from Latent Autoimmune Diabetes in Adults and late-onset type 1 diabetes. To facilitate C-peptide testing, we describe a quantitative point-of-care C-peptide test. C-peptide levels as low as 0.2 ng/ml were measurable in a fingerstick sample, and the test was accurate over a range of 0.17 to 12.0 ng/ml. This test exhibited a correlation of r = 0.98 with a high-sensitivity commercial ELISA assay and a correlation of r = 0.90 between matched serum and fingerstick samples.