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An Improved Bio-assay for the Determination of Long-Acting Thyroid Stimulator (LATS)

Department of Medicine, University of Adelaide, The Queen Elizabeth Hospital Woodville, South Australia
Division of Mathematical Statistics, Commonwealth Scientific and Industrial Research Organization Adelaide, South Australia

The bio-assay method for TSH described by Good and Stenhouse has been modified for the determination of long-acting thyroid stimulator (LATS). Using this design, which eliminates the factors of animal and day variation and the residual effects of the initial test doses by use of the mice on 2 successive days, and the standard response recommended by Kriss et al. (1964), the method has been found to have a sensitivity of 6.25 mU LATS, and an average index of precision () of 0.087. Linearity of the dose-response curve has been demonstrated over the range 6.25–400 mU of standard LATS serum. The reproducibility and precision obtained with this method appear to be better than with previous modifications of the McKenzie method. Applications of the method are briefly discussed. It is capable of detecting changes in circulating LATS and may be applied to the estimation of serum LATS activity in a large number of samples with a suitable computer program.

Received March 27, 1967.

Accepted July 19, 1967.