Document Detail

Systematic differences between commercial immunoassays for free thyroxine and free triiodothyronine in an external quality assessment program.
MedLine Citation:
PMID:  7923779     Owner:  NLM     Status:  MEDLINE    
Data collected in a national external quality assessment program for free thyroxine (fT4) and free triiodothyronine (fT3) were analyzed to evaluate the performance of 10 method/kits with 26 control samples distributed to approximately 170 laboratories. The control materials were normal serum pools, pooled sera supplemented with thyroid hormones, a pregnancy serum pool, serum pooled from patients with familial dysalbuminemic hyperthyroxinemia (FDH), and a normal serum pool progressively diluted. The between-laboratory variability (CV) was approximately constant in normal and supplemented pools for fT4 (15.3%) and fT3 (24.0%) but markedly increased in diluted, pregnancy, and FDH pools (21.9-35.2% for fT4 and 28.6-66.5% for fT3) because of increases in systematic between-kit differences in control samples with altered binding-protein capacity. Moreover, free hormone concentrations measured in progressively diluted sera averaged lower than in undiluted samples. This decrease of concentration was less for back-titration or labeled-antibody techniques and greater for labeled-analog methods; only the method involving adsorption to cross-linked dextran (Sephadex) was unaffected by dilution. Evaluation of the reproducibility of the method/kits showed between-assay, between-laboratory precision ranging from 7.8% to 17.0% for fT4 and from 9.8% to 20.3% for fT3.
G C Zucchelli; A Pilo; M R Chiesa; S Masini
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Clinical chemistry     Volume:  40     ISSN:  0009-9147     ISO Abbreviation:  Clin. Chem.     Publication Date:  1994 Oct 
Date Detail:
Created Date:  1994-11-07     Completed Date:  1994-11-07     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9421549     Medline TA:  Clin Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1956-61     Citation Subset:  IM    
CNR-Institute of Clinical Physiology, Pisa, Italy.
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MeSH Terms
Immunoassay / statistics & numerical data*
Quality Control
Reagent Kits, Diagnostic / statistics & numerical data*
Reproducibility of Results
Sensitivity and Specificity
Thyroxine / blood*
Triiodothyronine / blood*
Reg. No./Substance:
0/Reagent Kits, Diagnostic; 6893-02-3/Triiodothyronine; 7488-70-2/Thyroxine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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