Verification of the reference range for examination of thyroid parameters (TSH, fT3 a fT4) on the analyzer DxI 800 from Beckman Coulter
Abstract
Objective: Verification of the reference ranges given by the manufacturer for the determination of thyrotropin (TSH), free triiodothyronine (fT3), and free thyroxine (fT4) by immunoanalytical methods on a Beckman Coulter DxI 800 analyzer. Materials and methods: A total of 110 samples of healthy volunteer sera (55 men and 55 women) were measured to verify the reference interval for Beckman Coulter's Access TSH (3rd IS), Access Free T3, and Access Free T4 methods.
To exclude an unmanifested thyroid disease, proband sera were tested for the presence of thyroid peroxidase antibodies by the Access TPO Antibody method (Beckman Coulter). The resulting values were statistically evaluated using the robust CLSI C28-A3 method and the Box-Cox transformation in the MedCalc Statistical Software version 17.2.
Results: For the TSH method, a reference interval of 0.67 - 4.31 mIU/l (company figures 0.38 - 5.33 mIU/l) was established, for the fT3 method 4.99 - 7.49 pmol/l (company figures 3.8 - 6.0 pmol/l) and for the fT4 method 7.46 - 13.04 pmol/l (company figures 7.86 - 14.41 pmol/l). Conclusion: The reference interval specified for the TSH method by the reagents' manufacturer can be considered as verified and valid.
The reference interval we determined for the fT3 method does not match the reference interval recommended by the manufacturer - we found higher values for both the lower and upper reference limits. We would recommend adjusting this interval according to the measured data prior to routine implementation.
As for the fT4 determination method, we would suggest to shift the recommended reference interval towards lower values.