Critical appraisal of the influence of anti-Thyroglobulin on the measurement of Thyroglobulin and Thyroglobulin recovery
Robert Markewitz, Klaus-Peter Wandinger, Ralf JunkerAbstract
Background
Antibodies against Thyroglobulin (Anti-Tg) are known to be able to cause interferences in the measurement of Thyroglobulin (Tg). One method to quantify this interference is to measure Tg recovery after adding a known amount of Tg to the sample. The objective of this study was to examine the association between Tg, Tg-recovery and anti-Tg via a big data approach in real life data.
Methods
Results for Tg, anti-Tg and Tg recovery, measured in a high-throughput clinical laboratory via immunometric assays, were retroactively anonymized and analyzed. Specifically, the associations between Tg, anti-Tg and Tg recovery with one another and with the variables age and sex were statistically evaluated.
Results
15,609 samples were examined, of which only 98 samples exhibited disturbed Tg recovery. Of 66 of these, for which it was measured, 57 contained quantifiable and 28 elevated levels of anti-Tg. Anti-Tg was associated with decreased levels of Tg recovery and Tg itself (both: p < 0.0001), the strongest decreases being associated with elevated levels of anti-Tg. But even for elevated anti-Tg, median Tg-recovery was well within the reference range at 94 ± 10.4%. Effect sizes of all statistical comparissons were small to very small.
Conclusion
Tg recovery appears neither precise enough to detect interference of anti-Tg in the measurement of Tg on a single-specimen basis nor specific for it. This interference can nevertheless be detected statistically both for Tg recovery and for Tg, albeit with small effect sizes. Methods other than Tg recovery are needed to reliably detect disturbances in Tg measurement.