Comparison of fresh frozen serum to traditional proficiency testing material in a College of American Pathologists survey for ferritin, folate, and vitamin B12

Jay L. Bock, David B. Endres, Ronald J. Elin, Edward Wang, Bruce Rosenzweig, George G. Klee

Research output: Contribution to journalArticle

21 Scopus citations


Context. - Comparison of different analytical methods in proficiency surveys may be affected by the artificial nature of the survey material Objective. - To compare intermethod differences in proficiency survey results between 2 types of survey material, conventional proficiency testing material (PTM) and fresh frozen human serum (FFS), for 3 markers of anemia: ferritin, folate, and vitamin B12. Design. - Data were gathered from a 2003 survey event in the College of American Pathologists Ligand ("K") Series, in which the specimens to be tested by each participating laboratory included 1 vial of FFS and 2 vials of PTM with different analyte concentrations. The more than 1600 laboratories subscribing to the survey were not advised as to the nature of the specimens. Main Outcome Measures. - The bias of each method relative to the median of method means for each analyte and each type of survey material, and the interlaboratory co-efficient of variation for each method. Results. - For each of the 3 analytes, moderate to large method biases were observed. For ferritin, method biases correlated strongly between comparable PTM and FFS specimens (Spearman r = 0.863, P < .001), whereas virtually no correlation was found for folate (r = -0.224, P = .48), and a marginally significant correlation existed for B12 (r = 0.55, P = .049). Conclusions. - With ferritin, proficiency survey performance of PTM is similar to that of FFS, implying that method biases relate mainly to calibration. With folate and to a lesser extent with B12, PTM and FFS exhibit different method biases, implying that the biases reflect analyte heterogeneity and/or matrix effects.

Original languageEnglish (US)
Pages (from-to)323-327
Number of pages5
JournalArchives of Pathology and Laboratory Medicine
Issue number3
StatePublished - Mar 2005


ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Medical Laboratory Technology

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