SUPER-SENSITIVE ENZYME-IMMUNOASSAY FOR THYROID-STIMULATING HORMONE USING A NEW SYNERGISTIC ENHANCED CHEMILUMINESCENT END-POINT

The enhancers 1,1'-biphenyl-4-yl boronic acid and 4-iodophenol act syn ergistically in the horseradish peroxidase-catalysed oxidation of lumi nol. This concentration-dependent effect reduces background, increases signal and hence improves signal/background for detection of peroxida se. The same type of synergistic effect was found when 1,1'-biphenyl-4 -yl boronic acid was added to a commercial enhanced chemiluminescence signal reagent (Amerlite Signal Reagent). This synergistic enhanced ch emiluminescent endpoint (Amerlite Signal Reagent containing 1,1'-biphe nyl-4-yl boronic acid) for a horseradish peroxidase label has been tes ted in the Amerlite TSH and the Amerlite TSH-30 Ultrasensitive assays, The detection limit (mean of 20 replicates of the zero standard + 2SD ) in the Amerlite TSH assay was 0.0029 mIU/L. and in the Amerlite TSH- 30 Ultrasensitive assay the detection limit was 0.0005 mIU/L using the synergistic enhanced endpoint. Reassessment of the detection limit us ing a 1:40 dilution of the first standard (0.119 mIU/L) as the lowest assay standard gave a value of 0.0015 mIU/L for the Amerlite TSH-30 Ul trasensitive assay with the synergistic endpoint. A limited (n = 29) m ethod comparison using samples from euthyroid. hyperthyroid and hypoth yroid patients revealed excellent correlation between the conventional and synergistic TSH immunoassays.