{"doi":"10.1093/clinchem/hvae034","title":"Interlaboratory Comparison of Antibody-Free LC-MS/MS Measurements of C-peptide and Insulin","abstract":"BACKGROUND: The enhanced precision and selectivity of liquid chromatography-tandem mass spectrometry (LC-MS/MS) makes it an attractive alternative to certain clinical immunoassays. Easily transferrable work flows could help facilitate harmonization and ensure high-quality patient care. We aimed to evaluate the interlaboratory comparability of antibody-free multiplexed insulin and C-peptide LC-MS/MS measurements. METHODS: The laboratories that comprise the Targeted Mass Spectrometry Assays for Diabetes and Obesity Research (TaMADOR) consortium verified the performance of a validated peptide-based assay (reproducibility, linearity, and lower limit of the measuring interval [LLMI]). An interlaboratory comparison study was then performed using shared calibrators, de-identified leftover laboratory samples, and reference materials. RESULTS: During verification, the measurements were precise (2.7% to 3.7%CV), linear (4 to 15 ng/mL for C-peptide and 2 to 14 ng/mL for insulin), and sensitive (LLMI of 0.04 to 0.10 ng/mL for C-peptide and 0.03 ng/mL for insulin). Median imprecision across the 3 laboratories was 13.4% (inter-quartile range [IQR] 11.6%) for C-peptide and 22.2% (IQR 20.9%) for insulin using individual measurements, and 10.8% (IQR 8.7%) and 15.3% (IQR 14.9%) for C-peptide and insulin, respectively, when replicate measurements were averaged. Method comparison with the University of Missouri reference method for C-peptide demonstrated a robust linear correlation with a slope of 1.044 and r2 = 0.99. CONCLUSIONS: Our results suggest that combined LC-MS/MS measurements of C-peptide and insulin are robust and adaptable and that standardization with a reference measurement procedure could allow accurate and precise measurements across sites, which could be important to diabetes research and help patient care in the future.","journal":"Clinical Chemistry","year":2024,"id":438109,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":10,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9521,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":686035,"name":"Elisha Goonatilleke","orcid":null,"position":1,"is_corresponding":false},{"id":856651,"name":"Tai‐Tu Lin","orcid":null,"position":2,"is_corresponding":false},{"id":1248359,"name":"Maya Hatten-Beck","orcid":null,"position":3,"is_corresponding":false},{"id":766045,"name":"Michelle A. Emrick","orcid":"0000-0001-6943-4446","position":4,"is_corresponding":false},{"id":281288,"name":"Athena Schepmoes","orcid":"0000-0002-1365-106X","position":5,"is_corresponding":false},{"id":352736,"name":"Thomas Fillmore","orcid":"0000-0002-3763-589X","position":6,"is_corresponding":false},{"id":79569,"name":"Michael J. MacCoss","orcid":"0000-0003-1853-0256","position":7,"is_corresponding":false},{"id":884015,"name":"Salvatore Sechi","orcid":null,"position":8,"is_corresponding":false},{"id":257448,"name":"Kimia Sobhani","orcid":"0000-0002-9297-3445","position":9,"is_corresponding":false},{"id":700383,"name":"Randie R. Little","orcid":"0000-0001-6450-8012","position":10,"is_corresponding":false},{"id":832140,"name":"Kuanysh Kabytaev","orcid":"0000-0001-5219-5557","position":11,"is_corresponding":false},{"id":112291,"name":"Jennifer E. Van Eyk","orcid":"0000-0001-9050-148X","position":12,"is_corresponding":false},{"id":269960,"name":"Weijun Qian","orcid":"0000-0002-5393-2827","position":13,"is_corresponding":false},{"id":788,"name":"Andrew N. Hoofnagle","orcid":"0000-0002-6449-0243","position":14,"is_corresponding":false},{"id":289199,"name":"Annie Moradian","orcid":"0000-0002-0407-2031","position":0,"is_corresponding":true}],"reference_count":29,"raw_metadata":null,"created_at":"2026-07-19T02:00:38.888629Z","pmid":"38549041","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}