Background: RhTSH-Tg test is the gold standard to define the therapeutic strategy in DTC patients. Commonly the serum Tg peak is detected after 48/72 hours after the second injection. We observed several cases with a Tg that did not really increase but remained stable or showed anomalous small fluctuations. The interpretation of these “flat” tests represented a challenge in clinical practice and arose the question of a possible serum Tg interference. Aims: a) to verify the entity of this problem; b) to verify if the flat rhTSH-Tg tests could be related to heteropilic antibodies interference. Methods: After the exclusion of cases with circulating Tg autoantibodies, we reviewed 622 and 599 rhTSH-Tg tests performed in 2012 and 2010, respectively. Sera of flat rhTSH-Tg tests performed in 2012, kept at -20C, were revaluated by both using an ultrasensitive assay, (Beckman Coulter, Fullerton, CA, USA) and repeating the Tg determination with the standard immunometric assay (Diagnostic Products Corp., Los Angeles, CA) after dilution with a mouse serum. Results: 25/622 cases (4%) and 7/590 (1.2%) showed an anomalous Tg response to rhTSH. In 4/25(16%) cases serum Tg became negative afterdilution with mouse serum while in 17/25 (84%) a significant discrepancy between the Tg values determined with the two assays was observed. Conclusions: a) an increase of flat rhTH-Tg tests has been observed in 2012 with respect to 2010, with a prevalence of 4% in the last year; b) the serum Tg of flat tests were false positive likely due to heterophilic antibodies; c) a flat rhTSH-Tg test should not be considered as valid for taking therapeutic decisions and should be repeated after few months; d) the rhTSH stimulation can be used to identify putative false serum Tg values since no adequate response to the TSH stimulus will be observed in this case.
Recombinant Human Thyrotropin Stimulation Thyroglobulin (rhTSH-Tg) test can identify false serum tg due to heterophilic antibodies in differentiated thyroid cancer (DTC) patients
Matrone A;Gambale C;Taddei D;Molinaro E;Agate L;Bottici V;Viola D;Vitti P;Elisei R
2013-01-01
Abstract
Background: RhTSH-Tg test is the gold standard to define the therapeutic strategy in DTC patients. Commonly the serum Tg peak is detected after 48/72 hours after the second injection. We observed several cases with a Tg that did not really increase but remained stable or showed anomalous small fluctuations. The interpretation of these “flat” tests represented a challenge in clinical practice and arose the question of a possible serum Tg interference. Aims: a) to verify the entity of this problem; b) to verify if the flat rhTSH-Tg tests could be related to heteropilic antibodies interference. Methods: After the exclusion of cases with circulating Tg autoantibodies, we reviewed 622 and 599 rhTSH-Tg tests performed in 2012 and 2010, respectively. Sera of flat rhTSH-Tg tests performed in 2012, kept at -20C, were revaluated by both using an ultrasensitive assay, (Beckman Coulter, Fullerton, CA, USA) and repeating the Tg determination with the standard immunometric assay (Diagnostic Products Corp., Los Angeles, CA) after dilution with a mouse serum. Results: 25/622 cases (4%) and 7/590 (1.2%) showed an anomalous Tg response to rhTSH. In 4/25(16%) cases serum Tg became negative afterdilution with mouse serum while in 17/25 (84%) a significant discrepancy between the Tg values determined with the two assays was observed. Conclusions: a) an increase of flat rhTH-Tg tests has been observed in 2012 with respect to 2010, with a prevalence of 4% in the last year; b) the serum Tg of flat tests were false positive likely due to heterophilic antibodies; c) a flat rhTSH-Tg test should not be considered as valid for taking therapeutic decisions and should be repeated after few months; d) the rhTSH stimulation can be used to identify putative false serum Tg values since no adequate response to the TSH stimulus will be observed in this case.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
