Dosagem de tiroglobulina no seguimento de pacientes com carcinoma diferenciado de tiroide: interferentes, novos ensaios e aplicação clínica
Data
2022-05-12
Autores
Guastapaglia, Leila 
Orientadores
Biscolla, Rosa Paula Mello
Tipo
Tese de doutorado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Introdução: O Carcinoma Diferenciado de Tiroide (CDT) é a neoplasia tiroidiana mais comum e tem a dosagem de tiroglobulina (Tg) como principal marcador tumoral. A dosagem de Tg evoluiu muito ao longo dos anos, porém ainda apresenta desafios, apesar de os ensaios imunométricos usuais apresentarem ótimo desempenho. Objetivo: O objetivo principal dessa tese é avaliar o papel dos ensaios de Tg e os principais interferentes que resultam em valores falsamente baixos ou altos no seguimento de pacientes com CDT. Métodos: No primeiro manuscrito foram selecionados pacientes com doença estrutural e dosagem de Tg subestimadas pelo ensaio imunométrico para avaliação do papel de um novo ensaio competitivo policlonal (Tg-c) desenvolvido no Laboratório de Endocrinologia da UNIFESP com sensibilidade funcional de 20 ng/mL. Os resultados também foram comparados com os obtidos pelo ensaio por cromatografia líquida/espectrometria de massas (LC-MS/MS). No segundo projeto reportamos dois casos de interferência na dosagem de Tg por anticorpos heretófilos e os métodos usados para a investigação. No terceiro projeto foram selecionados 129 pacientes com CDT e anticorpos antitiroglobulina (AcATg) negativos e positivos para a comparação e avaliação do desempenho clínico de três ensaios diferentes de Tg (2 imunométricos e um ensaio por LC-MS/MS). Resultados: No primeiro projeto os pacientes que apresentavam doença estrutural e dosagens inapropriadas de Tg pelo ensaio imunométrico apresentaram níveis detectáveis de Tg-c variando entre 22 e 710 ng/mL. No segundo projeto, 2 pacientes que receberam critério de excelente resposta ao tratamento passaram a apresentar dosagens de Tg elevadas durante o seguimento (7,5 e 17 ng/mL) sem a detecção de doença estrutural. Realizamos diluição seriada nas amostras, que mostraram linearidade, porém as dosagens de Tg por outro ensaio imunométrico e por LC-MS/MS resultaram indetectáveis, comprovando a presença de interferentes que levaram a valores falsamente elevados. No terceiro projeto a correlação entre os dois ensaios imunométricos e o ensaio por LC-MS/MS foi substancial (r 0.950-0.985) nos pacientes com AcATg negativos e pobre entre os ensaios imunométricos e por LC-MS/MS (r 0.875-0.878) na presença de AcATg. 58.8% dos pacientes com doença estrutural e AcATg positivos apresentaram dosagem de Tg por LC-MS/MS indetectável. Apesar disso, nesses pacientes, a dosagem de Tg pelo ensaio imunométrico foi em torno de 30% mais baixa do que por LC-MS/MS. A sensibilidade em detectar doença estrutural nos pacientes com AcATg positivos foi maior pelo ensaio imunométrico do que por LC-MS/MS. Conclusões: Concluímos que os ensaios imunométricos ainda devem ser usados como método padrão para a dosagem de Tg, porém estão sujeitos a interferentes. Nessas situações, a dosagem de Tg por métodos diferentes como a LC-MS/MS e o ensaio competitivo policlonal ou por outro ensaio imunométrico podem apresentar benefícios.
Introduction: Differentiated Thyroid Carcinoma (DTC) is the most common thyroid neoplasm and has thyroglobulin (Tg) measurement as the main biochemical marker. The measurement of Tg has evolved a lot over the years, but it still poses challenges, despite the usual immunometric assays show great performance. Objective: The main aim of this is to evaluate the role of Tg assays and the main interferents that result in falsely low or high values of Tg in the follow-up of DTC patients. Methods: In the first manuscript, patients with structural disease and Tg levels underestimated by immunometric assay were selected to evaluate the role of a new polyclonal competitive assay (Tg-c) developed at the Endocrinology Laboratory of UNIFESP with a functional sensitivity of 20 ng/mL. The results were also compared with those obtained by the liquid chromatography/mass spectrometry (LC-MS/MS) assay. In the second study we report two cases of interference in the Tg measurement by heretophilic antibodies and the methods employed for the investigation. In the third manuscript, 129 DTC patients with negative and positive anti-thyroglobulin antibodies (TgAb) were selected for the comparison and evaluation of the clinical performance of three different Tg assays (2 immunometrics assays and LC-MS/MS assay). Results: In the first study, patients with structural disease and inappropriate levels of Tg by immunometric assay had detectable Tg-c levels ranging from 22 to 710 ng/mL. In the second manuscript, 2 patients who had criteria of excellent response to treatment began to present elevated Tg levels during follow-up (7.5 and 17 ng/mL) without the detection of structural disease. We performed serial dilution in the samples, which showed linearity, but the Tg measurements by another immunometric assay and by LC-MS/MS were undetectable, proving the presence of interferents that have led to falsely high values. In the third manuscript, the correlation between the two immunometric assays and the LC-MS/MS assay was substantial (r 0.950-0.985) in patients with negative TgAb and poor between the immunometric and LC-MS/MS assays (r 0.875-0.878) in the presence of TgAb. 58.8% of patients with structural disease and positive TgAb had undetectable Tg levels by LC-MS/MS. Despite this, in these patients, the Tg values obtained by the immunometric assay were around 30% lower than by LC-MS/MS. The sensitivity in detecting structural disease in patients with positive TgAb were higher by the immunometric assays than by LC-MS/MS. Conclusions: We conclude that immunometric assays should still be used as a standard method for measuring Tg, but they are prone to interference. In these situations, the measurement of Tg by different methods such as LC-MS/MS and the competitive polyclonal assay or by another immunometric assay may bring benefits.
Introduction: Differentiated Thyroid Carcinoma (DTC) is the most common thyroid neoplasm and has thyroglobulin (Tg) measurement as the main biochemical marker. The measurement of Tg has evolved a lot over the years, but it still poses challenges, despite the usual immunometric assays show great performance. Objective: The main aim of this is to evaluate the role of Tg assays and the main interferents that result in falsely low or high values of Tg in the follow-up of DTC patients. Methods: In the first manuscript, patients with structural disease and Tg levels underestimated by immunometric assay were selected to evaluate the role of a new polyclonal competitive assay (Tg-c) developed at the Endocrinology Laboratory of UNIFESP with a functional sensitivity of 20 ng/mL. The results were also compared with those obtained by the liquid chromatography/mass spectrometry (LC-MS/MS) assay. In the second study we report two cases of interference in the Tg measurement by heretophilic antibodies and the methods employed for the investigation. In the third manuscript, 129 DTC patients with negative and positive anti-thyroglobulin antibodies (TgAb) were selected for the comparison and evaluation of the clinical performance of three different Tg assays (2 immunometrics assays and LC-MS/MS assay). Results: In the first study, patients with structural disease and inappropriate levels of Tg by immunometric assay had detectable Tg-c levels ranging from 22 to 710 ng/mL. In the second manuscript, 2 patients who had criteria of excellent response to treatment began to present elevated Tg levels during follow-up (7.5 and 17 ng/mL) without the detection of structural disease. We performed serial dilution in the samples, which showed linearity, but the Tg measurements by another immunometric assay and by LC-MS/MS were undetectable, proving the presence of interferents that have led to falsely high values. In the third manuscript, the correlation between the two immunometric assays and the LC-MS/MS assay was substantial (r 0.950-0.985) in patients with negative TgAb and poor between the immunometric and LC-MS/MS assays (r 0.875-0.878) in the presence of TgAb. 58.8% of patients with structural disease and positive TgAb had undetectable Tg levels by LC-MS/MS. Despite this, in these patients, the Tg values obtained by the immunometric assay were around 30% lower than by LC-MS/MS. The sensitivity in detecting structural disease in patients with positive TgAb were higher by the immunometric assays than by LC-MS/MS. Conclusions: We conclude that immunometric assays should still be used as a standard method for measuring Tg, but they are prone to interference. In these situations, the measurement of Tg by different methods such as LC-MS/MS and the competitive polyclonal assay or by another immunometric assay may bring benefits.
Descrição
Citação
GUASTAPAGLIA, Leila. Dosagem de tiroglobulina no seguimento de pacientes com carcinoma diferenciado de tiroide: interferentes, novos ensaios e aplicação clínica. São Paulo, 2022. 98 f. Tese (Doutorado em Endocrinologia e Metabologia) – Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, 2022