Abstract
A new immunofluorometric assay (FIA) using an Europium labelled β-hTSH antibody was modified by TORRESANI for TSH determinations in dried blood specimens in 19851. In order to improve our TSH-Screening program done by radioimmunoassay (RIA), we further modified the assay procedure of FIA and compared both methods(FIA vs RIA) during a three-months-period covering 4100 newborns. Increasing the incubation period from 4 (I) to 16 hours (II) and the size of the sample from 3 mm(I)to 5 mm 0 (II) the following assay parameters improved:
Regression analysis revealed a low correlation between both methods for TSH < 20 μU/ml (r= 0.52) and a good (r=0.99) for TSH ≥20 μU/ml. Recall rate (TSH ≥ 20 μU/ml) was significantly lower (0.7 vs 1.7 %) and falsely elevated values occurred less frequently (0.2 vs 0.59 %). 3 cases of hypothyroidism were reliably detected by both methods. Conclusions: The handling of microtitration plates in FIA is more time consuming compared to common RIA procedures and asks for further automatization. However, a substantially lower recall rate improves the practicability and cost/benefit ratio of the TSH screening program.
1Clinical Chemistry, 1986, in press.
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Grueters, A., L'Allemand, D., Berger, B. et al. IMPROVED EFFICIENCY OF A TSH SCREENING PROGRAM BY INTRODUCTION OF A TIME RESOLVED FLUORO IMMUNOASSAY (DELFIAR). Pediatr Res 20, 1193 (1986). https://doi.org/10.1203/00006450-198611000-00120
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DOI: https://doi.org/10.1203/00006450-198611000-00120