In vitro assays to test the interference of anti-thyroglobulin antibodies on thyroglobulin measurement.
OBJECTIVE
To assess the interference of anti-thyroglobulin antibodies (TgAb) on serum thyroglobulin (Tg) measurement by in vitro experiments. Design Re-evaluation of Tg concentration after dilution with different TgAb-positive sera. On a first step, dilutions of the same Tg with different TgAb sera were performed and on a second step, different Tgs were diluted with the same TgAb serum.


METHODS
Tg measurements were performed using an immunometric (IMA) chemiluminescence assay. TgAb measurements were performed using two methods: immunoflurimetric assay (UNICAP 100) and IMA chemiluminescent assay (IMMULITE 2000).


RESULTS
Dilution of a known concentration of Tg with different TgAb-positive sera resulted in a variation of the final concentration of Tg ranging from -24 to -79%. A weak correlation was observed between the TgAb concentration and the percentage of the Tg deviation. Dilution of different Tgs with the same TgAb-positive serum illustrated how the same TgAb positive serum may determine a high interference or a neutral effect.


CONCLUSIONS
Present results suggest that the interference on Tg measurement observed in the presence of TgAb may result not only from the anti-thyroglobulin antibodies, but also from the thyroglobulin itself.
Madureira
Deolinda
D
Laboratório de Endocrinologia, Instituto Português de Oncologia de Lisboa, Francisco Gentil E.P.E., Rua Professor Lima Basto, 1099-023, Lisbon, Portugal. dmadureira@ipolisboa.min-saude.pt
Prazeres
Susana
S
Pedro
Márcia São
MS
Pereira
Teresa
T
Font
Ana Paula
AP
Bugalho
Maria João
MJ
D001323:Autoantibodies / Q000032:analysis / Q000097:blood* / Q000494:pharmacology*; D002138:Calibration; D005189:False Positive Reactions; D006801:Humans; D011863:Radioimmunoassay / Q000379:methods / Q000592:standards; D012107:Research Design; D012680:Sensitivity and Specificity; D013954:Thyroglobulin / Q000032:analysis* / Q000276:immunology
D001323:Autoantibodies; C006606:anti-thyroglobulin; D013954:Thyroglobulin