title: Continuous-flow enzyme immunoassay for thyroxine in serum.
abstract: We have evaluated a fully automated thyroxine assay involving the use of a homogeneous enzyme assay and a Technicon AutoAnalyzer II continuous flow system. Comparison by regression analysis with a thyroxine radioimmunoassay kit method gave a slope of 0.82 and a y-intercept of 7.81 micrograms/L (SE 0.86 microgram/L, r = 0.95). Within-run precision yielded CVs of 1.0-6.1%, between-day CVs were 2.0-14.4%; within-day precision showed a mean variance of 7.81 micrograms/L. Mean analytical recovery was 96.1%. Bilirubin, hemoglobin, and lipemia interfered with quantitation of results when their concentrations exceeded 50 mg/L, 300 mg/L, and 5 g/L, respectively. The reference interval for euthyroid status was calculated to be 50-110 micrograms/L. Sensitivity was 5.0 micrograms/L with a mean carryover of 1.65%. Current reagent and labor costs for enzyme immunoassay ($0.40) were less than for the manual radioimmunoassay procedure ($0.40) were less than for the manual radioimmunoassay procedure ($1.70). The assay is economical, simple to perform, and amenable to high-throughput thyroid screening in the routine laboratory.
mesh_terms: D001322:Autoanalysis; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood; D007037:Hypothyroidism / Q000097:blood; D007124:Immunoenzyme Techniques / Q000295:instrumentation; D013974:Thyroxine / Q000097:blood*
chemical_list: D013974:Thyroxine