PMID- 20470203 OWN - NLM STAT- MEDLINE DCOM- 20100920 LR - 20151119 IS - 1557-9077 (Electronic) IS - 1050-7256 (Linking) VI - 20 IP - 6 DP - 2010 Jun TI - Serum Basal thyroglobulin measured by a second-generation assay correlates with the recombinant human thyrotropin-stimulated thyroglobulin response in patients treated for differentiated thyroid cancer. PG - 587-95 LID - 10.1089/thy.2009.0338 [doi] AB - BACKGROUND: Recombinant human thyrotropin (rhTSH) stimulation is frequently used to assess the disease status of patients treated for differentiated thyroid cancer (DTC) when basal (unstimulated) thyroglobulin (b-Tg) is below the assay sensitivity limit. The objective of this study was to determine relationships between the b-Tg and the 72-hour rhTSH-stimulated Tg (rhTSH-Tg) using a second-generation immunochemiluminometric assay with a functional sensitivity of 0.05 ng/mL (microg/L). METHODS: Serum Tg was measured in paired b-Tg and rhTSH-Tg specimens from 1029 rhTSH tests performed on 849 TgAb-negative patients during long-term monitoring for DTC. RESULTS: Basal Tg correlated with rhTSH-Tg across b-Tg concentrations ranging from 0.05 to 1000 ng/mL (microg/L) (r = 0.85, p < 0.0001). The b-Tg concentration was unrelated to age, sex, basal TSH, 72-hour TSH, or the Tg fold response (rhTSH-Tg/b-Tg). Further, only 2/655 (0.3%) tests with b-Tg below 0.1 ng/mL (microg/L) had rhTSH-Tg above 2.0 ng/mL (microg/L) (2.9 and 3.8 ng/mL [microg/L], respectively). Thirty-three patients with three or more rhTSH tests performed over a 2- to 5-year period displayed high indexes of individuality for both the 72-hour TSH and the Tg fold response (indexes of individuality = 0.30 and 0.38, respectively). Basal Tg measured using a first-generation assay with a functional sensitivity of 0.9 ng/mL (microg/L) failed to reliably detect an rhTSH-Tg response above 2.0 ng/mL (microg/L). CONCLUSIONS: An rhTSH-Tg response above 2.0 ng/mL (microg/L) was highly unlikely when b-Tg was below 0.1 ng/mL (microg/L). Second-generation b-Tg measurements correlated with the degree of rhTSH-Tg stimulation and thus the likelihood of having rhTSH-Tg above the customary cut-off of 2.0 ng/mL (microg/L), whereas b-Tg measured by a first-generation assay did not. Correlations between four different assays showed that the use of a fixed Tg cut-off was influenced by assay selection. Patients receiving repetitive rhTSH tests had highly reproducible rhTSH-Tg/b-Tg fold responses, suggesting that repetitive testing is unnecessary and that second-generation measurement of b-Tg trends without rhTSH stimulation would be satisfactory for the long-term monitoring of most patients with DTC. FAU - Spencer, Carole AU - Spencer C AD - Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA. FAU - Fatemi, Shireen AU - Fatemi S FAU - Singer, Peter AU - Singer P FAU - Nicoloff, John AU - Nicoloff J FAU - Lopresti, Jonathan AU - Lopresti J LA - eng PT - Journal Article PL - United States TA - Thyroid JT - Thyroid : official journal of the American Thyroid Association JID - 9104317 RN - 0 (Recombinant Proteins) RN - 9002-71-5 (Thyrotropin) RN - 9010-34-8 (Thyroglobulin) SB - IM MH - Adolescent MH - Adult MH - Aged MH - Aged, 80 and over MH - Cell Differentiation MH - Humans MH - Luminescent Measurements/methods MH - Middle Aged MH - Neoplasm Recurrence, Local/diagnosis MH - Radioimmunoassay/methods MH - Recombinant Proteins MH - Reproducibility of Results MH - Thyroglobulin/*blood MH - Thyroid Neoplasms/*diagnosis/surgery MH - *Thyrotropin EDAT- 2010/05/18 06:00 MHDA- 2010/09/21 06:00 CRDT- 2010/05/18 06:00 PHST- 2010/05/18 06:00 [entrez] PHST- 2010/05/18 06:00 [pubmed] PHST- 2010/09/21 06:00 [medline] AID - 10.1089/thy.2009.0338 [doi] PST - ppublish SO - Thyroid. 2010 Jun;20(6):587-95. doi: 10.1089/thy.2009.0338.