Volledig artikel in The Journal of Clinical Endocrinology & Metabolism
DOI: http://dx.doi.org/10.1210/jc.2015-1967
Published Online: June 16, 2015
Thyroglobulin (Tg) testing revisited:
Tg assays, TgAb assays and correlation of results with clinical outcomes
Brian C. Netzel, Stefan K. G. Grebe, B. Gisella Carranza Leon, M. Regina Castro,
Penelope M. Clark, Andrew N. Hoofnagle, Carole A. Spencer, Adina F. Turcu,
and Alicia Algeciras-Schimnich
Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN (BCN, SKGG, AA-S),
Division of Endocrinology, Metabolism and Nutrition, Mayo Clinic, Rochester, MN (SKGG, GCL, RC,
AFT), Queen Elizabeth Hospital Birmingham, Birmingham, UK (PMC), Department of Laboratory
Medicine, University of Washington, Seattle, WA (ANH), University of Southern California, Los Angeles,
CA, USA (CAS)
Context:
Measurement of thyroglobulin (Tg) by mass spectrometry (Tg-MS) is emerging as a tool
for accurate Tg quantification in patients with anti-Tg autoantibodies (TgAb).
Objective:
To perform analytical and clinical evaluations of two Tg-MS in comparison to immunometric
Tg assays (Tg-IA) and Tg radioimmunoassays (Tg-RIA) in a cohort of thyroid cancer
patients.
Methods:
589 samples from 495 patients, 243 TgAb-/252 TgAb, were tested by Beckman, Roche,
Siemens-Immulite and Thermo-Brahms Tg and TgAb assays, two Tg-RIAs and two Tg-MS assays.
Results:
The frequency of TgAb was 58%, 41%, 27% and 39% for Roche, Beckman, Siemens-
Immulite and Thermo-Brahms, respectively. In TgAb- samples, clinical sensitivities and specificities
of 100% and 74–100%, respectively, were observed across all assays. In TgAb samples, all Tg-IA
demonstrated assay-dependent Tg under-estimation ranging from 41–86%. In TgAb samples,
the use of a common cut-off (0.5ng/mL) for the Tg-MS, 3 Tg-IA and USC-RIA, improved the sensitivity
for the Tg-MSs and Tg-RIAswhencompared to the Tg-IAs. Inupto22%ofTgAbcases, Tg-IAs
failed to detect Tg that was detectable by Tg-MS. In Tg-RIAs false-high biases were observed in
TgAb samples containing low Tg concentrations.
Conclusions:
Tg-IAs remain the method of choice for Tg quantitation in TgAb- patients In TgAb
patients with undetectable Tg by IA, Tg-MS will detect Tg in up to22%additional cases. Tg-RIA will
detect Tg in 35% cases, but a significant proportion of these will be clinical false positives. The
undetectable Tg-MS seen in 40% of TgAb cases in patients with disease need further
evaluation.
Table 1. Patient Demographics and Clinical Characteristics
Table 2. Concordance between Tg MS, IA and RIA in TgAb samples
Figure 1. Tg-IA bias in TgAb positive samples
Table 3. TgAb patients with Tg-MS FS* and immunoassay FS*
Figure 2. ROC curves and clinical sensitivity and specificity analysis for Tg-MS, Tg-IA and Tg-RIA.
Table 4. TgAb patients with Tg-MS FS* and RIA Tg FS*
Link naar volledig artikel:
http://press.endocrine.org/doi/pdf/10.1210/jc.2015-1967
.