Uniforme standarisatie ref.waarden TSH + FT4 op komst (IFCC)

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Lid geworden op: 08 nov 2014, 17:53

Uniforme standarisatie ref.waarden TSH + FT4 op komst (IFCC)

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Abstract
Standardization of Free Thyroxine Measurements Allows the Adoption of a More Uniform Reference Interval
Linde A.C. De Grande, Katleen Van Uytfanghe, Dries Reynders, Barnali Das, James D. Faix, Finlay MacKenzie, Brigitte Decallonne, Akira Hishinuma, Bruno Lapauw, Paul Taelman, Paul Van Crombrugge, Annick Van den Bruel, Brigitte Velkeniers, Paul Williams, Linda M. Thienpont

DOI: 10.1373/clinchem.2017.274407 Published July 2017

Abstract
Background:
The IFCC Committee for Standardization of Thyroid Function Tests intended to standardize free thyroxine (FT4) immunoassays.
We developed a Système International d'Unités traceable conventional reference measurement procedure (RMP) based on equilibrium dialysis and mass spectrometry. We describe here the latest studies intended to recalibrate against the RMP and supply a proof of concept, which should allow continued standardization efforts.


Methods:
We used the RMP to target the standardization and reference interval (RI) panels, which were also measured by 13 manufacturers. We validated the suitability of the recalibrated results to meet specifications for bias (3.3%) and total error (8.0%) determined from biological variation. However, because these specifications were stringent, we expanded them to 10% and 13%, respectively. The results for the RI panel were reported as if the assays were recalibrated. We estimated all but 1 RI using parametric statistical procedures and hypothesized that the RI determined by the RMP was suitable for use by the recalibrated assays.


Results:
Twelve of 13 recalibrated assays had a bias, meeting the 10% specification with 95% confidence; for 7 assays, this applied even for the 3.3% specification. Only 1 assay met the 13% total error specification. Recalibration reduced the CV of the assay means for the standardization panel from 13% to 5%. The proof-of-concept study confirmed our hypothesis regarding the RI but within constraints.


Conclusions:
Recalibration to the RMP significantly reduced the FT4 immunoassay bias, so that the RI determined by the RMP was suitable for common use within a margin of 12.5%.

Received for publication March 30, 2017.
Accepted for publication June 13, 2017.
© 2017 American Association for Clinical Chemistry
http://clinchem.aaccjnls.org/content/ea ... 017.274407



Volledig artikel
Harmonization of Serum Thyroid-Stimulating Hormone Measurements Paves the Way for the Adoption of a More Uniform Reference Interval
Linda M. Thienpont, Katleen Van Uytfanghe, Linde A.C. De Grande, Dries Reynders, Barnali Das, James D. Faix, Finlay MacKenzie, Brigitte Decallonne, Akira Hishinuma, Bruno Lapauw, Paul Taelman, Paul Van Crombrugge, Annick Van den Bruel, Brigitte Velkeniers, Paul Williams

DOI: 10.1373/clinchem.2016.269456 Published June 2017

Abstract
BACKGROUND:
The IFCC Committee for Standardization of Thyroid Function Tests developed a global harmonization approach for thyroid-stimulating hormone measurements.
It is based on a multiassay method comparison study with clinical serum samples and target setting with a robust factor analysis method. Here we describe the Phase IV method comparison and reference interval (RI) studies conducted with the objective to recalibrate the participating assays and demonstrate the proof-of-concept.


METHODS:
Fourteen manufacturers measured the harmonization and RI panel; 4 of them quantified the harmonization and first follow-up panel in parallel. All recalibrated their assays to the statistically inferred targets. For validation, we used desirable specifications from the biological variation for the bias and total error (TE). The RI measurements were done with the assays' current calibrators, but data were also reported after transformation to the new calibration status. We estimated the pre- and postrecalibration RIs with a nonparametric bootstrap procedure.


RESULTS:
After recalibration, 14 of 15 assays met the bias specification with 95% confidence; 8 assays complied with the TE specification. The CV of the assay means for the harmonization panel was reduced from 9.5% to 4.2%. The RI study showed improved uniformity after recalibration: the ranges (i.e., maximum differences) exhibited by the assay-specific 2.5th, 50th, and 97.5th percentile estimates were reduced from 0.27, 0.89, and 2.13 mIU/L to 0.12, 0.29, and 0.77 mIU/L.


CONCLUSIONS:
We showed that harmonization increased the agreement of results from the participating immunoassays, and may allow them to adopt a more uniform RI in the future.

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 hormone concentrations is an indispensable tool to confirm the disease, particularly because the clinical symptoms often resemble other disorders or are subtle in case of subclinical thyroid dysfunction (1, 2).

The main clinical scenarios for measurement of serum thyroid-stimulating hormone (TSH) 16 are screening for thyroid dysfunction, evaluation of thyroid hormone replacement for primary hypothyroidism, and assessment of suppressive therapy in patients with follicular cell-derived thyroid cancer. Professional practice guidelines incorporate laboratory testing of thyroid function in patient care (3–7).

Reference intervals (RI) reported along with the laboratory data are an integral part of the interpretation process (8, 9). Since many laboratory measurements are not yet comparable, RIs are typically established for each assay and are considered assay-specific.
For physicians who only use one laboratory and are aware of these technical issues, this practice is fine. However, those who request test results from different laboratories, are often faced with challenges owing to different RIs.

Assay-specific RIs are also problematic for patients who regularly move between geographic locations and/or are seen by different doctors (10). More generally, assay-specific measurement results prevent the development of modern public health standards, such as clinical guidelines quoting fixed decision limits and integration of electronic patient records in the healthcare system (11).
Paramount to the goal of using common RIs is the establishment of metrological traceability of in vitro diagnostic (IVD) medical devices—also called standardization (12–14).

As the IFCC Committee for Standardization of Thyroid Function Tests (C-STFT) members, we decided to focus our efforts on immunoassays for TSH and free thyroxine in partnership with the IVD industry (15).
Our premise was that, if possible, we should adhere to the concept for traceability recommended by the International Organization for Standardization (16).

Although a reference measurement procedure existed for free thyroxine, we considered this option for TSH unlikely and developed a pragmatic approach to harmonization rather than standardization (17, 18). To circumvent the often encountered commutability issues in establishing calibration traceability of IVD assays, it was a premise for C-STFT that harmonization should be done from a multiassay method comparison study with a panel of native and clinically relevant samples (19–21).

We developed a robust factor analysis method for estimation of the harmonization targets and demonstrated the equivalence of the approach to standardization to a reference measurement procedure (22, 23).

Here we report on behalf of the C-STFT the most recent Phase IV studies in our TSH harmonization efforts in which we demonstrate that establishing calibration traceability of commercially available immunoassays enables the adoption of a more uniform RI for TSH.


Gehele artikel:
http://clinchem.aaccjnls.org/content/63/7/1248.full.pdf



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Re: Uniforme standarisatie ref.waarden TSH + FT4 op komst (IFCC)

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