Clinical Chemistry, Vol 31, 1706-1709, Copyright © 1985 by American Association for Clinical Chemistry

Determination of thyrotropin in serum by time-resolved fluoroimmunoassay evaluated

HL Kaihola, K Irjala, J Viikari and V Nanto

We evaluated a new, highly sensitive time-resolved fluoroimmunoassay for thyrotropin (TSH) in serum. This direct immunometric "sandwich"- type assay involves two monoclonal antibodies against TSH, one immobilized, the other labeled with europium. Extremely high specific activity of the label and the use of labeled antibody in large excess make the method sensitive enough to measure TSH values falling below the normal reference interval. The standard curve is nearly linear over a wide range of TSH concentrations (standard concentrations range from 0.25 to 324 milli-int. units/L). The lowest concentration detectable was 25 micro-int. units/L. The CV for the assay was less than 6% at 0.5 milli-int. unit/L or higher, 11.3% at 0.1 milli-int. unit/L. For a CV of 10% the lower limit of the working range would be around 0.1 milli- int. unit/L. The interassay CV was 6.7 to 11.8% for TSH concentrations of 0.31 to 19.6 milli-int. units/L. The 95% confidence interval for sera from 111 healthy persons was 0.6-3.8 (range 0.3-3.8) milli-int. units/L. For hyperthyroid patients and thyroid cancer patients treated with thyroxin after thyroidectomy, serum TSH values were all below the reference interval (most were less than 25 micro-int. units/L).

The following articles in journals at HighWire Press have cited this article:

				C. T. Sawin, A. Geller, M. M. Kaplan, P. Bacharach, P. W. F. Wilson, and J. M. Hershman Low Serum Thyrotropin (Thyroid-Stimulating Hormone) in Older Persons Without Hyperthyroidism Arch Intern Med, January 1, 1991; 151(1): 165 - 168. [Abstract] [PDF]

				D. A. Ehrmann, M. Weinberg, and D. H. Same Limitations to the Use of a Sensitive Assay for Serum Thyrotropin in the Assessment of Thyroid Status Arch Intern Med, February 1, 1989; 149(2): 369 - 372. [Abstract] [PDF]