A high-throughput mass spectrometry assay to simultaneously measure intact insulin and C-peptide.
Level 5 - mechanism / opinion, no new human data
Laboratory analytical method validation study (bench research)
PubMed 26820765 · doi:10.1016/j.cca.2016.01.019
What was done
The authors developed a multiplexed liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay to simultaneously quantify intact insulin and C-peptide. Peptides were enriched from patient serum using magnetic bead-immobilized monoclonal antibodies on a robotic liquid handler. Eluted peptides were analyzed by LC-MS/MS using bovine insulin and stable isotopically-labeled (13C/15N) C-peptide as internal standards. Analytical measurement range, precision, and cross-reactivity against 5 commonly prescribed insulin analogs were assessed.
What was found
The assay achieved an analytical measurement range of 3 to 320 μIU/ml (18 to 1920 pmol/l) for insulin and 0.11 to 27.2 ng/ml (36 to 9006 pmol/l) for C-peptide. Intra- and inter-day assay variation was under 11% for both analytes. Among 5 diabetes-treating insulin analogs tested, only recombinant insulin lispro caused significant analytical interference for endogenous insulin measurement. No interferences were observed for C-peptide.
Why it matters
This high-throughput LC-MS/MS method provides simultaneous, automated quantification of insulin and C-peptide to help overcome the marked variability and lack of standardization among conventional immunoassays.
Limits
The abstract does not state the sample size (n) of patient sera evaluated. Clinical diagnostic thresholds, correlations with degrees of insulin resistance, and patient outcomes were not evaluated. The assay cannot accurately distinguish endogenous insulin in the presence of therapeutic insulin lispro.
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