Serum Thyroglobulin (Tg) assay by immunoradiometric methods (IRMA): comparison of concentrations obtained with Cisbio Bioassays vs Beckman Coulter kit in patients with differentiated thyroid cancer.

Abstract

Introduction: In clinical practice, Thyroglobulin is a tumor marker for the post-operative follow-up of differentiated thyroid cancer, provided that any thyroid residual remains are eliminated beforehand, either by simple total thyroidectomy, or most often supplemented by isotopic totalization with Iode131. The aim of this study were to compare serum Tg values measured with 02 kit manufacturers of immunoradiometric type (IRMA) and to evaluate their cost/effectiveness ratio. Methods: We included patients followed for differentiated thyroid cancer operated and irradiated with Iodine 131 at the nuclear medicine department of Tlemcen University Hospital. Their serum Thyroglobulin was dosed in the laboratory of the department with the Tg-IRMA kit of Cisbio Bioassays taken in this study as «Gold standard» and the Tg-IRMA kit of Beckman Coulter. Results: Ninety-nine (99) serums of patients with CDT were measured for Thyroglobulin. The correlation of the Thyroglobulin values obtained with the 02 kits is positive and significant (r= 0.98; p < 0.01). The equation of the regression line of Passing- Bablok is of type y = 0.7 x + 0 (with Y = Tg-IRMA Cisbio Bioassays and X = Tg-IRMA Beckman Coulter). The difference in the averages analyzed with the Bland-Altman diagram is = 0 (p > 0.05), indicating that there is no difference in the mean of Tg between the 02 kits. The analysis by ROC curve of the Tg-IRMA Beckman Coulter kit Thyroglobulin values at the threshold of 0.7 and 1 ng/mL finds respectively a sensitivity and a specificity of 100% and 93% with an area under the curve = 0.99. Conclusion: There is a strong correlation between Thyroglobulin concentrations obtained with the 02 kits, so a budget reduction in the management of our patients with diffrentiated thyroid cancer is possible, in favor of the Tg-IRMA kit of Beckman Coulter with a good cost/ efficiency ratio.