title: Multicenter evaluation of enhanced chemiluminescence labeled-antibody immunoassay (Amerlite-MAB) for free thyroxine.
abstract: The technical and diagnostic performance of the Amerlite-MAB enhanced luminescence assay for free thyroxine (FT4) was assessed in a multicenter evaluation trial. The euthyroid central 95% reference range for FT4 (1393 subjects) was 11.5-27.7 pmol/L (by cumulative frequency plot with two-tailed 2.5% cutoffs). Results (y) agreed with those of similar radioactive method (Amerlex-MAB FT4) (x): y = 1.06 x + 0.54, Sylx = 335.5, n = 235). Mean within-assay precision (CV) in six centers was 5.7% at 6 pmol/L and 2.6% at 51 pmol/L FT4; between-assay precision (CV) was 7.2% and 3.6%, respectively. Diagnostic performance was assessed in all patient groups usually encountered, including those with nonthyroidal illness and extreme binding-protein anomalies. In elderly euthyroid subjects, the proportion of above-normal FT4 values exceeded that in younger age-groups. These increases often accompanied normal estimates of thyrotropin and, in some cases, might have arisen by interference from medication that is taken more often by the elderly.
authors: Cardiff Laboratories, Kodak Clinical Diagnostics, Ltd., Amersham, UK.
authors: N D
authors: ND
authors: Christofides
authors: C P
authors: CP
authors: Sheehan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D001798:Blood Proteins / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood; D007037:Hypothyroidism / Q000097:blood; D007124:Immunoenzyme Techniques / Q000706:statistics & numerical data; D007223:Infant; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011786:Quality Control; D012016:Reference Values; D012680:Sensitivity and Specificity; D012727:Sex Characteristics; D013974:Thyroxine / Q000097:blood*
chemical_list: D001798:Blood Proteins; D013974:Thyroxine