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Unstimulated Highly Sensitive Thyroglobulin in Follow-up of Differentiated Thyroid Cancer Patients: A Meta-Analysis.
Giovanella L1, Treglia G, Sadeghi R, Trimboli P, Ceriani L, Verburg FA. J Clin Endocrinol Metab.
2014 Feb;99(2):440-7
PMID: 24285679
Serum thyroglobulin (Tg) is an indicator of
differentiated thyroid cancer (DTC) relapse. We conduced a meta-analysis of
published data about the diagnostic performance of highly sensitive serum Tg
(hsTg) during levothyroxine therapy in DTC follow-up. We performed a
comprehensive literature search of PubMed/MEDLINE and Scopus for studies
published until July 2013. Studies investigating the diagnostic performance of
basal hsTg in monitoring DTC were eligible if the serum Tg measurement had a
functional sensitivity >0.1 ng/mL; For each study, the number of
true-positive, false-positive, true-negative, and false-negative findings for
basal hsTg, considering stimulated Tg measurement as a reference standard, were
Pooled data demonstrated that the negative predictive value of hsTg was 97% and
99% considering a stimulated Tg measurement >1 ng/mL and >2 ng/mL as
cutoffs for positivity, respectively. Despite the high pooled sensitivity of
basal hsTg, the pooled specificity, accuracy, and positive predictive value
were insufficient to completely substitute for a stimulated Tg measurement.
Basal hsTg measurement has a very high
negative predictive value but an insufficient positive predictive value for
monitoring DTC patients. Therefore, a Tg stimulation test can be avoided in
patients with an undetectable basal hsTg
, whereas a stimulated Tg
measurement should be considered when hsTg levels are detectable.
Comment-This careful and useful meta-analysis found that a largo number of
reports had to be excluded for a variety of technical issues preventing
comparability. However, based on the acceptable studies, it was concluded that a
negative assay (no detectable TG)  during T4 suppression using a highly sensitive
assay with ability to detect 0.1ng/ml, in the absence of TG Ab, is a near perfect
predictor of a cancer-free state.
 Values between 0.1 and 1  ng/ml need to be followed by
a TSH-stimulated