Summary

A supersensitive ELISA was developed for measurement of thyroid-stimulating honnone (TSH) concentrations in serum using in-house rabbit polyclonal antisera and a commercial monoclonal antibody. The assay was optimised and validated by recovery, linearity and cross-reactivity experiments and further compared to other available assays andEQAS samples. Good precision was obtained with a working assay range of 0.2 to 100 mIU/L with <l 0 % coefficient of variation (CV) for both intra and interassay. The assay is highly sensitive and specific with a minimum detectable limit of 0.07 mIU/L and negligible cross-reactivities against LH, FSH, HCG and other pituitary peptides. Good conelations were obtained when compared to AbbotthTSHEIA (r=0.993; p<O.OOl; n=85) and NETRIA IRMA (r+0.995; p<O.OO1; n=76). The nonnal reference range established was 0.4 to 4.0 mIU/L (n=76). TSH levels in serum of thyrotoxic patients (n=83) were significantly lower (0.07 to 0.20 mIU/L, p<O.OOOl) and completely distinct from nonnal values thereby obviating the requirement of a TRH-stimulation test. Stability studies showed that coated wells can be stored at 4 QC for at least 2 months. This highly sensitive in-house hTSH ELISA which is cheap, stable and readily available is useful for diagnosis and management of patients with various thyroid disorders. Key words: ELISA, TSH, thyroid statu