NONSPECIFIC-BINDING AS A SOURCE OF ERROR IN THYROTROPIN RADIOIMMUNOASSAY WITH POLYETHYLENE-GLYCOL AS SEPARATING AGENT

  • 1 January 1980
    • journal article
    • research article
    • Vol. 26  (3) , 487-490
Abstract
The effects of nonspecific binding on thyrotropin values obtained by radioimmunoassay in which polyethylene glycol is used as precipitant were investigated. Differences in nonspecific binding among individual samples were significant (F-test, P < 0.01, range 5.5-14.1%). Nonspecific binding and total serum protein were directly correlated (r = 0.472, n = 59, P < 0.001). Nonspecific binding increased with increasing concentrations of globulins, but showed no relation to albumin concentration. If globulin concentration was < 15 g/l, precipitation of the antigen-antibody complex by polyethylene glycol was incomplete. The mean value for thyrotropin in sera from 67 healthy subjects was 2.7 (SD 0.3) mIU/l without individual serum nonspecific binding correction, significantly (P < 0.005) higher than that with nonspecific binding correction (1.6, SD 0.1, mIU/l). Evidently, intersample variations in nonspecific binding may cause significant errors under these conditions, which can be minimized by taking into account the individual nonspecific binding of each serum sample.

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