Adult references intervals for thyroid hormones using beckman coulter from Türkiye

INTRODUCTION: In this study, we aimed to establish reliable reference intervals (RIs) for free triiodothyronine (fT3), free thyroxine (fT4), and thyroid stimulating hormone (TSH) in our population using the Beckman Coulter UniCel DxI 800.
METHODS: We followed the Clinical Laboratory Standards Institute (CLSI) C28-A3 guidelines to calculate RIs through both direct (DRM) and indirect methods (IDM) and compared them with the RIs provided by Beckman Coulter UniCel DxI 800 Access® immunoassay system. High sensitive (h)TSH reagent used for TSH analyses. For DM, we excluded anti thyroid peroxidase (anti-TPO) or antithyroglobulin (anti-TG) positive samples, outliers, and samples with insufficient serum, resulting in final sample sizes of 420 for TSH, 411 for fT4, and 407 for fT3. For IDM, anti-TPO or anti-TG-positive samples, repeated samples, and outliers were excluded, resulting in fnal sample sizes of 2874 for TSH, 2072 for fT4, and 1163 for fT3.
RESULTS: Our study included 450 participants (225 females, 225 males) over the age of eighteen for DRM and utilized
data from the Laboratory Information System (LIS) between March 1, 2018, and February 28, 2020, for IDM. After excluding certain samples and outliers, the final sample sizes were determined. The reference intervals (RIs) for TSH, fT4, and fT3 were 0.42-4.18 mIU/L, 0.41-4.45 mIU/L, 0.57–1.08 ng/dL, 0.63–1.14 ng/dL, 2.62–4.01 pg/mL, and 2.72- 4.41 pg/mL for DRM and IDM, respectively.
DISCUSSION AND CONCLUSION: In conclusion, the RI that we will use for thyroid hormones in our laboratory is diferent from that provided by the manufacturer.