Free thyroxine and thyroid-stimulating hormone reference intervals in very low birth weight infants at 3-6 weeks of life with the Beckman Coulter Unicel DxI 800.

To establish reference intervals for thyroid stimulating hormone (TSH) and free thyroxine (FT4) at 3-6 weeks of age in very low birth weight (VLBW) infants with the Beckman Coulter Unicel DxI 800 by gender, birth weight (BW) and gestational age (GA) subgroups. A 4 year retrospective cohort of 308 VLBW infants (GA=27.9 weeks, BW=992.3g) was studied. All blood samples for TSH and FT4 were analyzed using the modified fTSH2 (TSH) and two-step competitive enzyme immunoassay (FT4). Reference intervals were evaluated according to the most recent Clinical and Laboratory Standards Institute (CLSI) guidelines. The study provides non-parametric 95% reference intervals with associated 90% confidence intervals for FT4 and TSH derived from 308 infants screened at a median of 31 days. The reference intervals for this population are TSH=1.14-11.04 mIU/L and FT4=10.9-21.4 pmol/L. TSH statistically differed according to birth weight (<1000 g vs 1000-1499 g) while FT4 differed according to gender and gestational age at time of testing (<32 weeks vs ≥ 32 weeks); however, these differences were not clinically significant and a single reference interval for each analyte is reported. The results of this study highlight the importance and complexity of establishing appropriate reference intervals for thyroid function testing for the preterm population.

Sun X ，Lemyre B ，Nan X ，Harrold J ，Perkins SL ，Lawrence SE ，Barrowman N ... -  《-》

Establishment of reference intervals for thyroid hormones in premature infants beyond the first week of life using Beckman Coulter Unicel DxI 800.

This 4-year retrospective cohort study aimed to establish reference intervals for free triiodothyronine (FT3), free thyroxine (FT4), and thyrotropin (TSH) in premature infants using the Beckman Coulter Unicel DxI 800 automated immunoassay system. Study subjects included 605 preterm infants with a gestational age of 26-36 weeks (corrected: 29-38 weeks). Pearson correlation was used to evaluate the association between hormone levels and gestational and corrected gestational ages. A nonparametric method was used to establish reference intervals based on corrected gestational age. FT3 and FT4 levels were positively correlated with gestational and corrected gestational ages, respectively. TSH levels were slightly negatively correlated with gestational and corrected gestational ages. FT3 significantly differed according to corrected gestational age (29-33 weeks vs 34-38 weeks); however, the difference was smaller than the reference change value (RCV) for the FT3 test. Thus, we combined the FT3 reference intervals into a single reference interval: 2.65-4.93 pmol/L (29-38 weeks). The reference intervals of FT4 and TSH were 11.20-24.97 pmol/L (29-38 weeks) and 1.01-10.14 mIU/L (29-38 weeks), respectively. Unlike those of full-term infants or adults, the reference intervals established in this study are applicable in premature infants. These results highlight the importance and complexity of establishing instrument-specific thyroid hormone reference intervals for preterm infants.

Wang Y ，Wu X ，Hong K ，Fu X ，Chen T ，Zhu M ，Ye H ... -  《-》

Reference intervals for thyroid-stimulating hormone (TSH) and free thyroxine (FT4) in infants' day 14-30 of life and a comparison with other studies.

Wong JSL ，Selveindran NM ，Mohamed RZ ，Zain FM ，Anas SS ，Hong JYH ... -  《-》

Establishment of trimester-specific thyroid stimulating hormone and free thyroxine reference interval in pregnant Chinese women using the Beckman Coulter UniCel™ DxI 600.

Zhang J ，Li W ，Chen QB ，Liu LY ，Zhang W ，Liu MY ，Wang YT ，Li WY ，Zeng LZ ... -  《-》

Reference range of thyroid hormones in very low birth weight infants at the time of discharge.

Chan DK ，Tagamolila V ，Ardhanari J ，Lim XY ，Wong J ，Yeo CP ... -  《-》