Abstract: CLINICAL SIGNIFICANCE OF TWO-STEP MAGNETIC RADIOIMMUNOASSAY FOR DETERMINING SERUM FREE T_3 AND FREE T_4Chen Bing(Isotope Department of maanshan Iron & Steel Complex, Anhui 243000)Abstract:The concentrations of the serum free T3 (FT3), free T4(FT4), total triodothgronine(TT3), totalthyroxine (TT4) and thyrotropin (TSH) are determined for 355 cases of normal persons, pregnantwomen and various thyropathetic patients. The normal values of FT3 and FT4 are 2. 0-8. 5 pmol/l,and 9. 5-26. 5 pmol/l, respectively. Neither FT3 nor FT4 is affected by the thyroxine combined withglobulin (TBG), which is of unique diagnostic value for those with variable TBG(such as pregnantwomen hyperthyroidism, hypothyroidism, etc. ), FT3 and FT4 are the most sensitive indices for diagnosts of hyperthyroidism, and hypothyroidism, respectively. In addition, FT3 and FT4 can greatly contribute to the observation of curative effectiveness under treatment.Keywords: magnetic separation two-step radioimmunoassay; FT3 FT4 thyropathy