Monitoring the stability of the standardization status of FT4 and TSH assays by use of daily outpatient medians and flagging frequencies

[helvella]

We would all wish that TSH and FT4 tests were absolutely standardised. That is, the results from any lab would be directly comparable to those from any other lab - worldwide.

My concern is that standardisation might not deliver what we hope. For example, if tests are improved (e.g. made more resistant to interference by antibodies or biotin), how do the changes implied by that get consistently incorporated into the standardised assays?

Clin Chim Acta. 2016 Apr 27. pii: S0009-8981(16)30157-7. doi: 10.1016/j.cca.2016.04.032. [Epub ahead of print]

Monitoring the stability of the standardization status of FT4 and TSH assays by use of daily outpatient medians and flagging frequencies.

De Grande LA1, Goossens K1, Van Uytfanghe K2, Das B3, MacKenzie F4, Patru MM5, Thienpont LM6; IFCC Committee for Standardization of Thyroid Function Tests (C-STFT).

Author information

1Department of Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium.

2Ref4U, Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium.

3Biochemistry and Immunology Laboratory, Kokilaben Dhirubhai Ambani Hospital and Medical Research Institute, Mumbai, India.

4Birmingham Quality/UK NEQAS, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK.

5Ortho-Clinical Diagnostics, Inc., Rochester, NY, USA.

6Department of Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Ottergemsesteenweg 460, 9000 Ghent, Belgium. Electronic address: [e-mail].

Abstract

Clinicians diagnose thyroid dysfunction based on TSH and FT4 testing. However, the current lack of comparability between assays limits the optimal use of laboratory data. The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) gave a mandate to the Committee for Standardization of Thyroid Function Tests (C-STFT) to resolve this limitation by standardization.

Recently, the Committee members and their partners felt ready to set the step towards the technical recalibration. However, before implementation, they were furthered by the Food and Drugs Administration (FDA) to develop a tool to assess the sustainability of the new calibration basis. C-STFT began to use 2 online applications, i.e., the "Percentiler" and "Flagger", with the intention to assess their utility for this purpose. The tools monitor the course of instrument-specific moving medians of outpatient results (Percentiler) and flagging rates (Flagger) from data of individual laboratories grouped by instrument/assay peer. They additionally document the mid- to long-term medians, hence, are quality indicators of stability of performance of both laboratories and peers/assays. Here, the first experiences built up in the pre-standardization phase are reported. They suggest the suitability of both applications to document the sustainability of the calibration basis in the post-standardization phase.

Copyright © 2016 Elsevier B.V. All rights reserved.

KEYWORDS:

Committee for Standardization of Thyroid Function Tests; International Federation of Clinical Chemistry and Laboratory Medicine; Median; Outpatient; Population variation; Quality indicator

PMID: 27132242 [PubMed - as supplied by publisher]

ncbi.nlm.nih.gov/pubmed/271...

As so often, the full paper is behind a paywall.

sciencedirect.com/science/a...

[diogenes Remembering]

Standardisation of assays is absolutely essential and inconsistency has been a scandal for over 30 years. The pity is that FT3 assays at the moment are not included. The way that authentication should be done is ideally to gather together all the extreme examples, for example, thyroid hormone binding protein levels from zero to high in all three of the individual proteins; patients with thyroxine (or T3)-binding antibodies in their blood; patients with unusual genetic variations in albumin that change its strength of binding T4 and T3; nonthyroidally ill patients; indeed all those that severely challenge any method. Then test all these. If any of these extreme categories fail, it is likely that there are general problems that will more or less impinge on the general population. That I think is the way forward, rather than massive examination of ordinary subjects.

[helvella Administrator Thyroid UK in reply to diogenes]

Thank you, diogenes.

Can't hep thinking that standardisation of the units used for reporting would help! The molarity versus mass divide that currently exists seems designed to cause mistakes and confusion. Nice thing about this step, it seems to me it could be done without linking it to any other changes.

[diogenes Remembering in reply to helvella]

Yes, the disparate use of ng/ml in the States (whose adoption of metric is about zero) and pmol/L elsewhere is a real problem. Why the US should resist metric is beyond me.