Comparison of serum free thyroxine measurements by chemiluminescence and equilibrium dialysis.
A study of 239 patients compared free thyroxine (FT4) measurements made by equilibrium dialysis (ED) with measurements made using the Magic Lite FT4 chemiluminescence (CI) immunoassay (Ciba Corning Immunodiagnostics). Patient groups: 41 normals; 27 hyperthyroid; 29 hypothyroid; 37 sick euthyroid; 10 chronic renal failure (CRF) and 25 pregnant patients; 13 oestrogen; 10 heparin; 12 salicylate; and 9 dilantin-treated patients; 3 lipaemic; 5 haemolysed; 6 hyperbilirubinaemic patients; 6 low thyroid binding protein (TBP) and 6 high TBP level patients. The two assays gave comparable results in most groups. Both assays tended to give elevated values in heparinized patients but FT4-ED results were more obviously affected. Pregnant patients and women on oral oestrogen had higher mean values with FT4-ED. In both assays the sick euthyroid and CRF patients had mean FT4 values similar to healthy euthyroid patients; the range of values in sick euthyroid and CRF patients was similar in both assays but wider than in healthy euthyroid patients. A supplemental study of 81 unselected acutely ill patients using FT4-Cl alone confirmed the wider range of values to be anticipated in sick euthyroid patients.
Bigos
S T
ST
Division of Endocrinology, Maine Medical Center, Portland, Maine 04102.
MacLean
J
J
Butler
B
B
D000328:Adult; D003956:Dialysis; D005069:Evaluation Studies as Topic; D005260:Female; D006493:Heparin; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008163:Luminescent Measurements; D008875:Middle Aged; D011247:Pregnancy; D012016:Reference Values; D013959:Thyroid Diseases / Q000097:blood; D013974:Thyroxine / Q000097:blood*
D006493:Heparin; D013974:Thyroxine