A comparison of human chorionic gonadotropin-related components in fresh frozen serum with the proficiency testing material used by the College of American Pathologists

George J. Knight, Glenn E. Palomaki, George G. Klee, William E. Schreiber, Lawrence A. Cole

Research output: Contribution to journalReview article

5 Scopus citations


Context. - As part of a College of American Pathologists (CAP) proficiency testing survey, a comparison is made between human chorionic gonadotropin (hCG) results from an actual patient pool and a similarly targeted artificial sample. The goal is to gain insight into the possible source(s) of bias attributable to the proficiency testing material (PTM) with a view toward creating more appropriate survey materials. Objective. - To compare hCG and related variants in a pool of fresh frozen sera (FFS) with that found in PTM. Design. - The 2003 CAP K/KN-A Survey included a FFS specimen along with admixtures of PTM. The FFS (K-02) and 1 PTM admixture (K-01) had similar mean hCG values. Five hCG-related analytes were measured on these 2 samples by a reference laboratory. Participants. - Approximately 1800 clinical laboratories and diagnostic test kit manufacturers participated in the K/ KN-A Survey. Main Outcome Measures. - Method imprecision (coefficient of variation) and method bias (relative difference between peer group mean and all-method median) were computed for the 2 samples. Differences were evaluated with respect to hCG-related analytes levels. Results. - All-method hCG results were 12.9 mIU/mL (12.9 IU/L) for the PTM material and 21.6 mIU/ml (21.6 IU/L) for the FFS material. Method biases for 14 manufacturers were greater for PTM than for FFS (-40% to +35% and -16% to +23%). Twelve of 14 methods had higher coefficients of variation on PTM. Total hCG and free β hCC measurements by the reference laboratory were 14.1 mIU/ mL (14.1 IU/L) for the PTM material and 18.5 mIU/mL (18.5 U/L) for the FFS material (FFS), and 2.4 (PTM) and 0.7 (FFS) mIU/mL (2.4 and 0.7 IU/L), respectively. On a molar basis, free β represented 17% and 4% of the total hCG, respectively. Levels of hyperglycosylated hCG, nicked hCG, and β core fragment were not measurable in either sample. Conclusions. - It is unlikely that the hCC added to the PTM is the source of the increased bias and variability. The main difference is a 3-fold increase in free β found in the PTM, but methods previously found to strongly react with free β were not systematically elevated. The biases between manufacturers found for the FFS specimen are likely attributable to calibration differences.

Original languageEnglish (US)
Pages (from-to)328-330
Number of pages3
JournalArchives of Pathology and Laboratory Medicine
Issue number3
StatePublished - Mar 1 2005


ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Medical Laboratory Technology

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