ABSTRACT
Thyroglobulin (Tg) levels are important to predict recurrence in differentiated thyroid cancer patients.However, false-positive results can hence the request of unnecessary tests and treatments. We reported two cases of interference in thyroglobulin measurement and the workup to investigate them. Both patients achieved an excellent response to therapy after total thyroidectomy and one patient had also received radioiodine treatment. During the follow-up, Tg levels increased and there was no evidence of recurrent disease in the imaging studies. The Tg levels by the Access platform were positive but the results by Elecsys platform and LC-MS/MS were undetectable, leading to the hypothesis of heterophile antibodies (HAbs) interference. The possibility of HAbs interference must be considered when the Tg levels do not fit in the clinical picture. The measurement of Tg by another immunoassay or by LC-MS/MS may be useful in these situations.
Subject(s)
Thyroglobulin , Thyroid Neoplasms , Humans , Antibodies, Heterophile , Iodine Radioisotopes/therapeutic use , Chromatography, Liquid , Tandem Mass Spectrometry , Thyroid Neoplasms/therapy , ThyroidectomyABSTRACT
SUMMARY Thyroglobulin (Tg) levels are important to predict recurrence in differentiated thyroid cancer patients. However, false-positive results can hence the request of unnecessary tests and treatments. We reported two cases of interference in thyroglobulin measurement and the workup to investigate them. Both patients achieved an excellent response to therapy after total thyroidectomy and one patient had also received radioiodine treatment. During the follow-up, Tg levels increased and there was no evidence of recurrent disease in the imaging studies. The Tg levels by the Access platform were positive but the results by Elecsys platform and LC-MS/MS were undetectable, leading to the hypothesis of heterophile antibodies (HAbs) interference. The possibility of HAbs interference must be considered when the Tg levels do not fit in the clinical picture. The measurement of Tg by another immunoassay or by LC-MS/MS may be useful in these situations.
ABSTRACT
Serum testosterone in its total or free form, is a highly valuable diagnostic test and is available in the great majority of clinical laboratories. This reality was possible due to the development of simple and direct assays, adaptable to large automatic systems. Recent publications have called attention to the limitations of these simplified methodologies, mainly in samples with low concentration, as women and children. In this paper we present results obtained using a reference method based on high performance liquid chromatography and tandem mass spectrometry (HPLC/MS-MS) and its comparison with those obtained with a commercial routine immunoassay (electrochemiluminescent assay, ECLIA). Methods were compared in total testosterone measurement (n = 213), as well as in free testosterone evaluation based on calculation including sex hormone-binding protein (SHBG) levels (n = 135). Values obtained with ECLIA were significantly higher, with more marked dispersion in low concentration. This phenomenon is clearer when presented as a Bland-Altman plot. Difficulties in the implementation of reference methods as the one presented are discussed, as well as the necessity of caution in the interpretation of values obtained with routine assays, a matter of several publications in recent literature.
Subject(s)
Chromatography, High Pressure Liquid/methods , Luminescent Measurements/methods , Tandem Mass Spectrometry/methods , Testosterone/blood , Adolescent , Adult , Aged , Child , Data Interpretation, Statistical , Electrochemistry , Female , Humans , Male , Middle Aged , Reference Values , Sensitivity and Specificity , Sex Hormone-Binding Globulin/analysis , Young AdultABSTRACT
A dosagem de testosterona sérica, total ou fração livre, é metodologia de alto valor diagnóstico e encontra-se disponível na maioria dos laboratórios clínicos. Esta disponibilidade foi possível pelo desenvolvimento de metodologias simples e diretas, adaptáveis a plataformas de dosagem automatizada. Uma série de publicações recentes tem alertado quanto às limitações destas metodologias, em especial em amostras com baixas concentrações, como mulheres e crianças. Neste trabalho serão apresentados os resultados do emprego de uma metodologia de referência, fundamentada em cromatografia líquida de alta performance e espectrometria de massa em tandem (HPLC/MS-MS), e sua comparação com uma dosagem de rotina (ensaio eletroquimioluminescente - ECLIA). Os métodos são comparados tanto na dosagem de testosterona total (n = 213) quanto na determinação de testosterona livre calculada com base na determinação da testosterona total e da proteína carregadora de hormônios sexuais (SHBG) (n = 135). Os valores obtidos com o ECLIA são significativamente mais elevados, sendo a dispersão mais nítida em soros com baixas concentrações. Tal fenômeno fica mais claro quando apresentado na forma de gráficos de Bland-Altman. Neste trabalho são discutidas as dificuldades de implementação de uma metodologia de referência, como a apresentada, e a convivência com as metodologias de rotina, bem como a literatura recente sobre o assunto.
Serum testosterone in its total or free form, is a highly valuable diagnostic test and is available in the great majority of clinical laboratories. This reality was possible due to the development of simple and direct assays, adaptable to large automatic systems. Recent publications have called attention to the limitations of these simplified methodologies, mainly in samples with low concentration, as women and children. In this paper we present results obtained using a reference method based on high performance liquid chromatography and tandem mass spectrometry (HPLC/MS-MS) and its comparison with those obtained with a commercial routine immunoassay (electrochemiluminescent assay, ECLIA). Methods were compared in total testosterone measurement (n = 213), as well as in free testosterone evaluation based on calculation inclu-ding sex hormone-binding protein (SHBG) levels (n = 135). Values obtained with ECLIA were significantly higher, with more marked dispersion in low concentration. This phenomenon is clearer when presented as a Bland-Altman plot. Difficulties in the implementation of reference methods as the one presented are discussed, as well as the necessity of caution in the interpretation of values obtained with routine assays, a matter of several publications in recent literature.
