Measurement of thyroglobulin by liquid chromatography-tandem mass spectrometry in serum and plasma in the presence of antithyroglobulin autoantibodies.
Clin Chem
; 59(6): 982-90, 2013 Jun.
Article
en En
| MEDLINE
| ID: mdl-23396140
ABSTRACT
BACKGROUND:
Measurement of serum thyroglobulin (Tg) is used to monitor patients after treatment for differentiated thyroid carcinoma (TC). Difficulty in using Tg as a biomarker of the recurrence of TC in many patients stems from the presence of endogenous anti-Tg autoantibodies (Tg-AAbs), which can interfere with immunoassays (IAs) and cause false-negative results.METHODS:
We enriched Tg from serum samples using rabbit polyclonal anti-Tg antiserum and protein precipitation. Unrelated proteins were partially depleted in the process. Enriched proteins were then denatured, reduced, and digested with trypsin after the addition of a winged internal standard peptide. A Tg-specific tryptic peptide was purified by immunoaffinity extraction and analyzed by 2-dimensional LC-MS/MS. Instrument cycle time was 6.5 min per sample.RESULTS:
The lower limit of quantification was 0.5 ng/mL (0.76 fmol/mL dimer). Total imprecision of triplicate measurements in serum samples over 5 days was <10%. Comparison with a commercial IA using serum samples free of Tg-AAb (n = 73) showed Deming regression, IA = 1.00 * LC-MS/MS - 2.35, r = 0.982, standard error of the estimate (S(y|x)) = 9.52. In a set of Tg-AAb-positive samples that tested negative for Tg using IA (n = 71), concentrations determined by LC-MS/MS were ≥0.5 ng/mL in 23% of samples (median 1.2, range 0.7-11 ng/mL).CONCLUSIONS:
The introduced method has acceptable performance characteristics for use in clinical diagnostic applications. The most substantial disagreement between methods was observed in Tg-AAb-positive samples with concentrations <2 ng/mL (determined with LC-MS/MS). The affinity-assisted enrichment strategy used for Tg in this method should be applicable to other biomarkers that have endogenous autoantibodies.
Texto completo:
1
Colección:
01-internacional
Asunto principal:
Plasma
/
Autoanticuerpos
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Tiroglobulina
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Análisis Químico de la Sangre
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Espectrometría de Masas en Tándem
Límite:
Adolescent
/
Child
/
Child, preschool
/
Female
/
Humans
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Infant
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Male
Idioma:
En
Revista:
Clin Chem
Asunto de la revista:
QUIMICA CLINICA
Año:
2013
Tipo del documento:
Article
País de afiliación:
Estados Unidos