Multicentre clinical evaluation of the new highly-sensitive Elecsys® thyroglobulin II assay in patients with differentiated thyroid carcinoma

Abstract

Objective

A highly-sensitive thyroglobulin assay (Elecsys^® Tg II, Roche Diagnostics, Penzberg, Germany) has become available for monitoring patients with differentiated thyroid cancer (DTC). Here we evaluated the clinical performance of Elecsys^® Tg II assay in a multicentre patients series and compare it with the established Access^® Tg assay (Beckman Coulter, Brea, US).

Design

Retrospective analysis on prospectively selected patients in four thyroid cancer referral centres with uniform DTC management.

Participants

All DTC cases diagnosed, treated and followed-up in four tertiary referral centres for thyroid cancer since January 2005 (n=1456) were retrieved and predefined selection criteria were applied to prevent relevant enrollment biases. A series of 204 patients was finally selected for the present study.

Measurements

Samples had been stored at -80° C. Tg was measured by fully automated immunometric Elecsys^® Tg II and Access^® Tg assays in a centralized laboratory.

Results

Two hundred and four DTC were finally included. Of these, 10.8% had structural recurrence (sREC) and 81.4% showed no evidence of disease (NED) at the end of follow-up. There was a significant analytical bias between methods that cannot be used interchangeably. Using ROC curve analysis, the best basal and rhTSH-stimulated Tg cutoffs to detect sREC were 0.41 μg/L and 1.82 μg/L for Elecsys^® and 0.36 μg/L and 1.62 μg/L for Access^® assay, respectively. Using Cox proportional hazard regression, Tg was the only independent predictor of cancer relapse.

Conclusions

Using appropriate assay-specific cutoffs, the clinical performance of the Elecsys^® Tg II assay was comparable to that provided by the well-established Access^® Tg assay.

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