Standardization of C-Peptide Measurements

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

doi:10.1373/clinchem.2007.101287

Cited by 83 publications

(75 citation statements)

References 13 publications

(11 reference statements)

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“…This protocol has also been validated to be suitable for triglycerides and HDL cholesterol (15 ) and for creatinine (16 ). The C37A protocol has not been validated to produce samples that are commutable with patient samples for other analytes but represents the best available approach and has been used to prepare single-donor serum samples and pools for several investigations of the trueness of measurement procedures for several analytes (17)(18)(19)(20)(21). Thienpont et al found that processing of serum (e.g., sterile filtration, storage before aliquoting and freezing) may disturb the equilibrium between free and protein-bound thyroid hormone and hence jeopardize the commutability of a reference material prepared even from sera that has been subjected to minimal processing (22 ).…”

Section: Preparation Of Samples Intended To Be Commutablementioning

confidence: 99%

Proficiency Testing/External Quality Assessment: Current Challenges and Future Directions

et al. 2011

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BACKGROUND: Proficiency testing (PT), or external quality assessment (EQA), is intended to verify on a recurring basis that laboratory results conform to expectations for the quality required for patient care.CONTENT: Key factors for interpreting PT/EQA results are knowledge of the commutability of the samples used and the process used for target value assignment. A commutable PT/EQA sample demonstrates the same numeric relationship between different measurement procedures as that expected for patients' samples. Noncommutable PT/EQA samples frequently have a matrix-related bias of unknown magnitude that limits interpretation of results. PT/EQA results for commutable samples can be used to assess accuracy against a reference measurement procedure or a designated comparison method. In addition, the agreement of the results between different measurement procedures for commutable samples reflects that which would be seen for patients' samples. PT/EQA results for noncommutable samples must be compared to a peer group mean/ median of results from participants who use measurement procedures that are expected to have the same or very similar matrix-related bias. Peer group evaluation is used to asses whether a laboratory is using a measurement procedure in conformance to the manufacturer's specifications and/or in conformance to other laboratories using the same technology. A noncommutable PT/EQA sample does not give meaningful information about the relationship of results for patients' samples between different measurement procedures.

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Section: Preparation Of Samples Intended To Be Commutablementioning

confidence: 99%

Proficiency Testing/External Quality Assessment: Current Challenges and Future Directions

et al. 2011

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“…In conclusion, there are ongoing efforts to harmonise C-peptide immunoassays, including the development of isotope-dilution liquid chromatography-mass spectrometry (LCMS) reference methods [10,11] and a certified reference material [12] for the calibration of these methods, in addition to investigations into the use of panels of serum calibrators for standardisation/harmonisation [13,14]. It is anticipated that the First International Standard will complement these efforts to aid in the standardisation and harmonisation of C-peptide immunoassays.…”

Section: Discussionmentioning

confidence: 99%

Preparation, calibration and evaluation of the First International Standard for human C-peptide

Moore

Dougall

Ferguson

et al. 2017

Clinical Chemistry and Laboratory Medicine (CCLM)

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Background: Measurement of C-peptide by immunoassay contributes to the diagnosis of a number of disorders related to β cell function. Stocks of the current international reference reagent (IRR) for C-peptide, used to calibrate these immunoassays, are exhausted, and this report summarises the international study to establish a replacement World Health Organization (WHO) international standard (IS) to maintain the availability of a globally available reference material and support efforts to standardise C-peptide assays. Methods: The study was conducted in three phases; phase I involved the assignment of a value to a primary calibrant in mass units by amino acid analysis and phase II applied this value to the calibration of a candidate standard, 13/146, by reversed phase high-performance liquid chromatography (RP-HPLC) assay. In phase III, the candidate standard was compared to the first IRR by current immunoassays to assess its suitability to serve as an IS. Results: Calibration of the candidate standard by RP-HPLC gave a final estimated content of 8.64 μg/ampoule with expanded uncertainty of 8.21-9.07 μg/ampoule (95% confidence; k = 2.45). The candidate standard also appears sufficiently stable to serve as an IS, based on HPLC analysis of accelerated thermal degradation samples of 13/146, and was also shown to have appropriate immunological activity. A difference in bias approach was used to assess the commutability of 13/146 with human serum and urine samples. With the exception of two laboratories, the candidate standard demonstrated commutability with respect to the serum and urine samples included in this study. Conclusions:The candidate standard, 13/146, is suitable to serve as the First International Standard for human

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“…Thus, the reason for the low slope observed using serum samples in the comparison between the ARCHITECT and the Elecsys C-Peptide assays cannot be attributed to different standards being used. However, it might be related to different assay formats and the antibodies used (26).…”

Section: Discussionmentioning

confidence: 99%

Diagnostic performance of the ARCHITECT C-Peptide immunoassay

Schultess¹,

Duren²,

Martens³

et al. 2009

Clinical Chemistry and Laboratory Medicine

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Background: Measurement of C-peptide under standardized conditions provides a sensitive and wellestablished assessment of b-cell function. We describe the analytical and clinical validation of an automated, microparticle-based chemiluminescent immunoassay method. The assay is designed to measure C-peptide in human serum, plasma and urine. Methods: Assay performance characteristics such as precision and recovery were measured according to protocols established by the Clinical Laboratory Standards Institute (CLSI). A reference range study was conducted. Analytical sensitivity and specificity, interfering substances, recovery, and linearity studies were performed. Method comparison, against the ADVIA Centaur C-Peptide assay (Siemens), was evaluated with clinical specimens from patients with abnormal insulin secretion. Results: The detection limit for this assay was 0.01 ng/mL. Functional sensitivity (inter-assay imprecision F20%) was 0.015 ng/mL at a coefficient of variation (%CV) of 11.2%. Total imprecision was below 6.5% CV. The assay was linear upon dilution. Comparison with the ADVIA Centaur C-Peptide assay yielded a correlation coefficient (r) of 0.99. Conclusions:The ARCHITECT C-Peptide assay measures C-peptide rapidly, accurately, and precisely in human serum, plasma and urine. It provides useful improvements for b-cell function testing and for evaluating the clinical status of a patient in combination with other diabetes markers. Clin Chem Lab Med 2009;47:834-41.

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Standardization of C-Peptide Measurements

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.

Cited by 83 publications

References 13 publications

Proficiency Testing/External Quality Assessment: Current Challenges and Future Directions

Proficiency Testing/External Quality Assessment: Current Challenges and Future Directions

Preparation, calibration and evaluation of the First International Standard for human C-peptide

Diagnostic performance of the ARCHITECT C-Peptide immunoassay

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