Standardization of C-peptide measurements

Randie R. Little, Curt L. Rohlfing, Alethea L. Tennill, Richard W. Madsen, Kenneth S. Polonsky, Gary L. Myers, Carla J. Greenbaum, Jerry P. Palmer, Eduard Rogatsky, Daniel T. Stein

Research output: Contribution to journalArticle

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Abstract

BACKGROUND: C-peptide is a marker of insulin secretion in diabetic patients. We assessed within- and between-laboratory imprecision of C-peptide assays and determined whether serum calibrators with values assigned by mass spectrometry could be used to harmonize C-peptide results. METHODS: We sent 40 different serum samples to 15 laboratories, which used 9 different routine C-peptide assay methods. We also sent matched plasma samples to another laboratory for C-peptide analysis with a reference mass spectrometry method. Each laboratory analyzed 8 of these samples in duplicate on each of 4 days to evaluate within- and between-day imprecision. The same 8 samples were also used to normalize the results for the remaining samples to the mass spectrometry reference method. RESULTS: Within- and between-run CVs ranged from <2% to >10% and from <2% to >18%, respectively. Normalizing the results with serum samples significantly improved the comparability among laboratories and methods. After normalization, the differences among laboratories in mean response were no longer statistically significant (P = 0.24), with least-squares means of 0.93-1.02. CONCLUSIONS: C-peptide results generated by different methods and laboratories do not always agree, especially at higher C-peptide concentrations. Within-laboratory imprecision also varied, with some methods giving much more consistent results than others. These data show that calibrating C-peptide measurement to a reference method can increase comparability between laboratories.

Original languageEnglish (US)
Pages (from-to)1023-1026
Number of pages4
JournalClinical Chemistry
Volume54
Issue number6
DOIs
StatePublished - Jun 1 2008

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C-Peptide
Standardization
Mass spectrometry
Mass Spectrometry
Assays
Serum
Least-Squares Analysis
Insulin
Plasmas

ASJC Scopus subject areas

  • Clinical Biochemistry

Cite this

Little, R. R., Rohlfing, C. L., Tennill, A. L., Madsen, R. W., Polonsky, K. S., Myers, G. L., ... Stein, D. T. (2008). Standardization of C-peptide measurements. Clinical Chemistry, 54(6), 1023-1026. https://doi.org/10.1373/clinchem.2007.101287

Standardization of C-peptide measurements. / Little, Randie R.; Rohlfing, Curt L.; Tennill, Alethea L.; Madsen, Richard W.; Polonsky, Kenneth S.; Myers, Gary L.; Greenbaum, Carla J.; Palmer, Jerry P.; Rogatsky, Eduard; Stein, Daniel T.

In: Clinical Chemistry, Vol. 54, No. 6, 01.06.2008, p. 1023-1026.

Research output: Contribution to journalArticle

Little, RR, Rohlfing, CL, Tennill, AL, Madsen, RW, Polonsky, KS, Myers, GL, Greenbaum, CJ, Palmer, JP, Rogatsky, E & Stein, DT 2008, 'Standardization of C-peptide measurements', Clinical Chemistry, vol. 54, no. 6, pp. 1023-1026. https://doi.org/10.1373/clinchem.2007.101287
Little RR, Rohlfing CL, Tennill AL, Madsen RW, Polonsky KS, Myers GL et al. Standardization of C-peptide measurements. Clinical Chemistry. 2008 Jun 1;54(6):1023-1026. https://doi.org/10.1373/clinchem.2007.101287
Little, Randie R. ; Rohlfing, Curt L. ; Tennill, Alethea L. ; Madsen, Richard W. ; Polonsky, Kenneth S. ; Myers, Gary L. ; Greenbaum, Carla J. ; Palmer, Jerry P. ; Rogatsky, Eduard ; Stein, Daniel T. / Standardization of C-peptide measurements. In: Clinical Chemistry. 2008 ; Vol. 54, No. 6. pp. 1023-1026.
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N2 - BACKGROUND: C-peptide is a marker of insulin secretion in diabetic patients. We assessed within- and between-laboratory imprecision of C-peptide assays and determined whether serum calibrators with values assigned by mass spectrometry could be used to harmonize C-peptide results. METHODS: We sent 40 different serum samples to 15 laboratories, which used 9 different routine C-peptide assay methods. We also sent matched plasma samples to another laboratory for C-peptide analysis with a reference mass spectrometry method. Each laboratory analyzed 8 of these samples in duplicate on each of 4 days to evaluate within- and between-day imprecision. The same 8 samples were also used to normalize the results for the remaining samples to the mass spectrometry reference method. RESULTS: Within- and between-run CVs ranged from <2% to >10% and from <2% to >18%, respectively. Normalizing the results with serum samples significantly improved the comparability among laboratories and methods. After normalization, the differences among laboratories in mean response were no longer statistically significant (P = 0.24), with least-squares means of 0.93-1.02. CONCLUSIONS: C-peptide results generated by different methods and laboratories do not always agree, especially at higher C-peptide concentrations. Within-laboratory imprecision also varied, with some methods giving much more consistent results than others. These data show that calibrating C-peptide measurement to a reference method can increase comparability between laboratories.

AB - BACKGROUND: C-peptide is a marker of insulin secretion in diabetic patients. We assessed within- and between-laboratory imprecision of C-peptide assays and determined whether serum calibrators with values assigned by mass spectrometry could be used to harmonize C-peptide results. METHODS: We sent 40 different serum samples to 15 laboratories, which used 9 different routine C-peptide assay methods. We also sent matched plasma samples to another laboratory for C-peptide analysis with a reference mass spectrometry method. Each laboratory analyzed 8 of these samples in duplicate on each of 4 days to evaluate within- and between-day imprecision. The same 8 samples were also used to normalize the results for the remaining samples to the mass spectrometry reference method. RESULTS: Within- and between-run CVs ranged from <2% to >10% and from <2% to >18%, respectively. Normalizing the results with serum samples significantly improved the comparability among laboratories and methods. After normalization, the differences among laboratories in mean response were no longer statistically significant (P = 0.24), with least-squares means of 0.93-1.02. CONCLUSIONS: C-peptide results generated by different methods and laboratories do not always agree, especially at higher C-peptide concentrations. Within-laboratory imprecision also varied, with some methods giving much more consistent results than others. These data show that calibrating C-peptide measurement to a reference method can increase comparability between laboratories.

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