Harmonization of Thyroid-stimulating Hormone Immunoassays Reagents

Given the prevalence and gravity of thyroid disorders, timely diagnosis, initiation, and monitoring of therapy are important to restrict the impact of the disease on public health. Measurement of serum thyroid stimulating hormone (TSH) concentrations is an indispensable tool to confirm the disease and clinical management.

Reference intervals (RI) reported along with the laboratory data are an integral part of the interpretation process. Since many laboratory measurements are not yet comparable, RIs are typically established for each assay and are considered assay-specific. In this context, physicians who request test results from different laboratories are faced with challenges owing to different RIs. Assay-specific RIs are also problematic for patients who are seen by different doctors/different countries and more generally, assay-specific measurement results limit the development of modern public health standards.

Paramount to the goal of using common RIs is the establishment of metrological traceability of in vitro diagnostic (IVD) medical devices-also called standardization. As the International Federation of Clinical Chemistry (IFCC) Committee for Standardization of Thyroid Function Tests (C-STFT) members, the investigators decided to focus efforts on immunoassays for TSH in partnership with the IVD industry.

Although a reference measurement procedure existed for free thyroxine, the investigators considered this option for TSH unlikely and developed a pragmatic approach to harmonization rather than standardization.

Harmonization is important in order to guarantee comparability of results obtained in different laboratories. The harmonization process is conducted by assigning target values to a large set of samples, based on the results obtained by as many IVD-manufacturers as possible (ref 2). Important here is the fact that these samples must cover the full measuring range of a TSH assay, and so it is necessary to include samples from people with thyroid disease.

The primary objective of the study is the constitution of blood samples collection from patients with thyroid disorders in order to harmonize several commercially available immunoassays used for the determination of thyroid hormone concentrations in the blood.