Sandrine Donadio-Andréi1, Karim Chikh2,3,4, Christine Heuclin5, Elisabetta Kuczewski2, Anne Charrié2,3,4, Anne-Sophie Gauchez4,6,7,8, Catherine Ronin1. 1. Siamed'Xpress, Hôtel Technologique Morandat, Gardanne, France. 2. CARMEN-INSERM U1060, Université Claude Bernard Lyon 1, Hospices Civils de Lyon, France. 3. CARMEN-INSERM U1060, Université Claude Bernard Lyon 1, Faculté de Médecine et de Maïeutique Lyon Sud - Charles Mérieux, Oullins, France. 4. Société Française de Médecine Nucléaire, Groupe de Biologie Spécialisée, Centre Antoine Béclère, Paris, France. 5. Laboratoire du Service de Médecine Nucléaire, BioSIMS Technologies, Seine Biopolis II, Rouen, France. 6. Laboratoire du Service de Médecine Nucléaire, Centre Hospitalier de Chambéry, Chambéry, Grenoble, France. 7. Pôle de Biologie, Centre Hospitalier et Universitaire de Grenoble, Grenoble, France. 8. Pôle de Biologie, Centre Hospitalier et Universitaire de Grenoble, UMR-S INSERM 1037, Grenoble, France.
Abstract
OBJECTIVES: Measuring protein markers with variable glycosylation, such as thyroid-stimulating hormone (TSH), with high accuracy is not an easy task. Despite highly sensitive third-generation tests, discrepancies among TSH assays still remain unsolved and are the focus of important standardization efforts. Earlier work from our group showed that a lack of similarity in epitope expression between standards and samples may account for discordant hormone measurements. In this study, we aimed at producing a glycoengineered TSH with serum-type glycosylation and compared its immunological behavior to that of the international standards. STUDY DESIGN: Recombinant glycoengineered TSH (rgTSH) was produced in glycoengineered Chinese hamster ovary cells to express a highly sialylated TSH and tested in newly designed assays. Two groups of assays targeting defined epitopes were constructed and TSH levels were estimated in a panel of 84 clinical samples (2.1-22.4 mIU/l) based on the use of the current 3rd IS 81/565, the 1st IRP 94/674 and rgTSH calibrations. RESULTS: Calibration based on rgTSH was found to significantly reduce the percentage difference means of assays compared to the pituitary standard. We also found that a switch from a mIU/l (3rd IS 81/565) to ng/l (rgTSH) basis can be established within the normal as well as in the mid to upper normal range of TSH levels. Of interest, TSH assays targeting the main immunogenic region displayed variable TSH values, indicating that, in this region, epitopes should be defined for assays to deliver similar values. CONCLUSIONS: A glycoengineered TSH with serum-type glycosylation proved to be a new calibrator efficient in harmonizing TSH values.
OBJECTIVES: Measuring protein markers with variable glycosylation, such as thyroid-stimulating hormone (TSH), with high accuracy is not an easy task. Despite highly sensitive third-generation tests, discrepancies among TSH assays still remain unsolved and are the focus of important standardization efforts. Earlier work from our group showed that a lack of similarity in epitope expression between standards and samples may account for discordant hormone measurements. In this study, we aimed at producing a glycoengineered TSH with serum-type glycosylation and compared its immunological behavior to that of the international standards. STUDY DESIGN: Recombinant glycoengineered TSH (rgTSH) was produced in glycoengineered Chinese hamster ovary cells to express a highly sialylated TSH and tested in newly designed assays. Two groups of assays targeting defined epitopes were constructed and TSH levels were estimated in a panel of 84 clinical samples (2.1-22.4 mIU/l) based on the use of the current 3rd IS 81/565, the 1st IRP 94/674 and rgTSH calibrations. RESULTS: Calibration based on rgTSH was found to significantly reduce the percentage difference means of assays compared to the pituitary standard. We also found that a switch from a mIU/l (3rd IS 81/565) to ng/l (rgTSH) basis can be established within the normal as well as in the mid to upper normal range of TSH levels. Of interest, TSH assays targeting the main immunogenic region displayed variable TSH values, indicating that, in this region, epitopes should be defined for assays to deliver similar values. CONCLUSIONS: A glycoengineered TSH with serum-type glycosylation proved to be a new calibrator efficient in harmonizing TSH values.