Groen, A.H. (2014) The clinical value of high-sensitive thyroglobulin assay in the follow-up of patients with differentiated thyroid carcinoma. thesis, Medicine.
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Abstract
Introduction: Thyroglobulin (Tg) is a specific marker for differentiated thyroid carcinoma (DTC). In our clinic, serum Tg is measured using an immunoradiometric two-step assay (IRMA-Tg, Thermo Fisher, Germany). Measurement of unstimulated serum Tg (Tg-on) using a high-sensitive assay (hs-Tg, Thermo Fischer) is proposed to replace TSH-stimulated Tg measurements (Tg-off) in the follow-up of patients with DTC. The first aim was to investigate if the hs-Tg-on measurement is able to predict patients with an IRMA-Tg-off >1.0 ng/ml and <1.0 ng/ml. The second aim of this study is to investigate whether the use of the high-sensitive Tg assay, in a cohort of patients with a recurrence of DTC, lead to earlier detection of recurrences. Methods: Between March 2006 and November 2013, serum Tg-on and Tg-off were routinely measured using the IRMA-Tg, during the follow-up of patients with DTC. Samples from 99 consecutive patients were remeasured using the hs-Tg assay, when Tg antibodies and distant metastases at initial presentation were absent, the stimulated TSH was >15 mU/L and the samples were available. Assay results from 98 patients were available. To answer the second aim, 8 patients with recurrent disease were included and matched with 3 patients in remission. Two serum samples preceding the clinical recurrence and one at moment of proven recurrence were re-measured using the hs-Tg assay. Three recent serum samples were selected from the follow-up of the control group. Assay results of both the hs-Tg assay and Tg-IRMA were compared using Passing and Bablok analysis and the functional sensitivity was determined. The assays and the groups were evaluated with paired Wilcoxon signed rank tests and a ROC curve was calculated, using IBM SPSS for Windows version 20. Results: Comparison of both assays using Passing and Bablok analysis revealed the following conversion factor: IRMA-Tg = 0.82x hs-Tg, with a slope statistically different from 1. Functional sensitivity for IRMA-Tg and hs-Tg were 0.30 ng/ml and 0.07 ng/ml respectively. Thirty-one out of 98 patients had an IRMA-Tg-off >1.0 ng/ml. Eleven out of these patients had a previous hs-Tg-on measurement >1.0 ng/ml and 10 with the IRMA-Tg-on. Forty-three patients showed a hs-Tg-on <0.15 ng/ml, the highest value that results in a 100% specificity. When remeasured, none had an IRMA-Tg-off measurement >1.0 ng/ml (negative predictive value (NPV) 100%). However, 66 patients revealed an IRMA-Tg-on measurement <0.15 ng/ml 3 months after ablation, 9 had an IRMA-Tg-off measurement >1.0 ng/ml (NPV 86.4%) 6 months after ablation. Three out of 8 recurrences could be detected earlier (3, 12 and 12 months) with the hs-Tg-on measurement, when the same cut-off value (1.0 ng/ml) was used. The IRMA-Tg detected 5 patients and the hs-Tg assay detected 4 patients with a Tg value >1,0 ng/ml. None of the control samples demonstrated false positive measurements using the hs-Tg-on measurement. Conclusion: Our study shows that there is no additional value of the hs-Tg-on assay 3 months after ablation in comparison to the IRMA-Tg-off measurements 6 months after ablation to predict patients with an IRMA-Tg-off >1.0 ng/ml. However, the hs-Tg-on measurement may be useful to predict patients with an IRMA-Tg-off <1.0 ng/ml. In this small number of patients the hs-Tg assay does not seem to have additional value in the earlier detection of recurrences. More data are needed to draw final conclusions regarding the use of this hs-Tg assay to prevent a subset of patients from thyroid hormone withdrawal.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Links, Prof. Dr. T. P. and Plukker, Prof. Dr. J.T.M. and Muller Kobold, Dr. A.C. and Klein Hesselink, Drs. M.S. |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 11:02 |
| Last Modified: | 25 Jun 2020 11:02 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/2191 |
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