Evaluation of the first automated thyroglobulin assay

The aim of this study was to investigate technical and analytical performan ce of the first automated thyroglobulin (Tg) assay (DPC-Immulite(R); Diagno stic Products Corporation, Los Angeles, USA). In imprecision studies using several human serum pools ranging from 21 to 58 replicates, a coefficient o f variation of 9.0 % was obtained at a mean Tg concentration of 0.84 ng/ml and of 6.1 % at a Tg concentration of 62.1 ng/ml. In a method comparison wi th a non-automated assay (BRAHMS LUMItest Tg(R), BRAHMS, Berlin, Germany) u sing 383 sera of 303 patients with thyroid carcinoma, regression analysis a ccording to Passing and Bablock yielded in the following equation: Immulite Tg=1.6 x BRAHMS Tg - 0.1 ng/ml (Pearson's r=0.979). Sera obtained from 59 patients with thyroid carcinoma enabled comparative f ollow-up studies; in all cases qualitative agreement was found with regard to increase or decrease of serum Tg; in eight cases, however, Tg was detect ed with the Immulite assay but not with the BRAHMS assay. Further follow-up proved the presence of thyroid tissue in these patients. From these and fu rther methodological data (dilution linearity, interference studies, carry- over study, high-dose hook properties, and short report time) it is conclud ed that the DPC-Immulite Tg assay meets the requirements of routine diagnos tic use.