New neonatal thyrotropin enzyme immunoassay with fluorimetric detection: comparison with time-resolved...

This short communication compares a novel fluorimetric microplate enzyme immunoassay (FEIA) with a commercial time-resolved fluoroimmunoassay for the determination of thyrotropin in dried blood spots. The evaluation was performed using a retrospective study design with newborn blood samples from three screening centres. Non-parametric Spearman rank correlation analysis revealed highly significant positive correlation between methods: rs = 0.465, p < 0.0001 (Hannover), rs = 0.659, p < 0.0001 (Minsk), rs = 0.755, p < 0.0001 (Helsinki). Wilcoxon signed rank test performed for paired FEIA and time-resolved fluoroimmunoassay showed that the results obtained by both tests represented the same distribution (p < 0.0001). The new method, using fluorimetric detection, can be performed with the instrumentation commonly used for the screening of congenital hypothyroidism and phenylketonuria. Results are obtained within three to four hours after arrival of the sample in the laboratory. Preliminary evaluation indicates the method to be a suitable alternative to time-resolved fluoroimmunoassay for neonatal thyroid function screening.