Effective October 23, 2018, methodology for the Thyroglobulin (THY), Thyroglobulin Antibody (TGAB), and Thyroid Peroxidase Antibody (TPOAB) tests changed from Siemens Immulite 2000 to Beckman Access DXI. 

This change in technology will allow us to fulfill a frequent client request for greater sensitivity in Thyroglobulin monitoring, with the lower limit of our reportable Thyroglobulin detection range moving from 1 ng/mL to 0.2 ng/mL.  As with any change in tumor marker methodology, however, quantitative results obtained from the previous Immulite platform may not be directly comparable to the quantitative result obtained from the DXI platform, and this change will involve an update in Thyroglobulin reference ranges.  

As a result of this platform change, there will also be an update in the reference ranges for Thyroglobulin Antibody and Thyroid Peroxidase Antibody tests.  Published data indicate that, although all commercially available TGAB and TPOAB antibody assays show good analytical performance relative to WHO reference standards, there is well documented method-to-method variation. ¹ Results from the Immulite to the DXI should be compared based on the negative or positive interpretation of these antibody values.  More recent generations of technology have substantially improved harmonization between methods, ² and our in-house validation showed good concordance for positive and negative results for these assays, but as noted above, any two methods for this type of testing may not be directly interchangeable, and a small number of “high negative” samples from the previous Immulite platform may test as “low positive” on the new DXI.