Commutability of NIST SRM 1955 Homocysteine and Folate in Frozen Human Serum With Selected Total Homocysteine Immunometric or Enzymatic Assays

Published

March 1, 2008

Author(s)

B C. Nelson, Christine M. Pfeiffer, Ming Zhang, David L. Duewer, Katherine E. Sharpless, Katrice Lippa

Abstract

Background: The National Institute of Standards and Technology (NIST) and the Centers for Disease Control and Prevention (CDC) have recently developed Standard Reference Material (SRM) 1955 Homocysteine and Folate in Frozen Human Serum with certified values for total homocysteine (tHcy). NIST and the CDC have performed an international, interlaboratory assessment of the commutability of SRM 1955. Methods: tHcy was measured in 20 patient sera and in 3 levels of SRM 1955 using selected immunometric and enzymatic assays. Liquid chromatography/tandem mass spectrometry (LC/MS/MS) was utilized as the reference assay. Fourteen independent tHcy assays were evaluated. An errors-in-variables (EIV) statistical analysis model based on weighted linear regression was utilized to assess the commutability of SRM 1955 using a limit of 3.0 for the normalized residuals.Results: Normalized residuals ranged from -2.65 to 2.19 for SRM 1955 samples. The mean interlaboratory/interassay imprecision (CV) was 5% for patient specimens and ranged from 3% to 7% for SRM 1955 samples. The mean intraassay imprecision (CV) ranged from 1% to 13% for the tested assays. Orthogonal residuals, as a descriptor of assay accuracy, ranged from 0.29 to 7.71 and from 0.20 to 2.22 for patient specimens and SRM 1955 samples, respectively. Conclusions: Based on the EIV statistical model, SRM 1955 was shown to be commutable with all of the tested assays. Incorporation of NIST SRM 1955 within the global tHcy clinical measurement system will establish traceability for routine clinical measurements and improve the accuracy and performance of tHcy measurement procedures.

Citation

Clinica Chimica ACTA

Volume

395

Pub Type

Journals

Keywords

cardiovascular disease, commutability, enzymatic assay, homocysteine, immunoassay, SRM, tandem mass spectrometry

Citation

Nelson, B. , Pfeiffer, C. , Zhang, M. , Duewer, D. , Sharpless, K. and Lippa, K. (2008), Commutability of NIST SRM 1955 Homocysteine and Folate in Frozen Human Serum With Selected Total Homocysteine Immunometric or Enzymatic Assays, Clinica Chimica ACTA (Accessed April 23, 2024)