Establishment Of Reference Interval For Thyroid Function During Pregnant Women In Qujing Area

Objective(s):To establish the reference value areas of thyroid function in Qujing area and the instrumentation method used for each stage of pregnancy,and also to analyze the changes of thyroid hormones in pregnant women with pregnancy.Methods:In accordance with the recommended criteria of the National Academy of Sciences Institute of Clinical Biochemistry(NACB),A total of 610pregnant women who attended the endocrine clinic of Qujing First People’s Hospital from December 2021 to October 2022 were collected as study subjects,and all of them underwent thyroid function tests,including thyroid stimulating hormone(TSH),serum free thyroxine(FT4),serum free triiodothyronine(FT3),thyroid peroxidase antibodies(TPOAB)and thyroglobulin antibodies(TGAB),of which 438 were included in the area for establishing the reference values of thyroid function in pregnancy in this region,including 145 cases in early pregnancy,149 cases in mid pregnancy and 144 cases in late pregnancy.SPSS26.0 software was used for all date analyses,the measurement data conforming to normal or approximately normal distribution were expressed as mean±standard deviation,one-way ANOVA was used between multiple groups,and the statistic was expressed as F.The categorical vaviables were expressed as frequency(rate/composition ratio),and the comparison between groups was analyzed byχ~2test or Fisher’s exact probability method.Serum TSH,FT3 and FT4 reference values were selected with 95%confidence intervals,with 2.5 th as the lower limit and 97.5 th as the upper limit.P<0.05 was considered to be statistically significant.Results:1.No statistically significant difference was found in the age of each stage,and no significant difference was seen in the comparison of the age of T1,T2 and T3stages,P>0.05.2.The FT3 reference value areas in each gestational period were:T13.337-5.601pmol/L;T2 2.97-5.285pmol/L;T3 2.395-4.7pmol/L.FT3 gradually decreased with the increase of gestational weeks after pregnancy,and the difference was statistically significant in each gestational period,P<0.05.3.The FT4 reference value areas in each gestational period were:T1 period9.897-18.813pmol/L;T2 period 8.153-17.522pmol/L;T3 period 6.706-16.89pmol/L.FT4 showed a gradual decrease with the increase of gestational weeks in the post-gestational period,and the difference between gestational periods was statistically significant,P<0.05.4.The TSH reference values in each gestational period were 0.115-4.137m IU/L in T1;0.259-4.302m IU/L in T2;0.372-4.898m IU/L in T3.The TSH gradually increased with the increase of gestational weeks after pregnancy,and the difference was statistically significant in each gestational period,P<0.05.5.The differences between the prevalence of SCH diagnosed by the criteria established in this study and those recommended by the 2017 ATA,Roche kit and2019 Chinese guidelines were statistically significant(P<0.001).If the upper limit of TSH reference value recommended by 2017 ATA was used for the diagnosis of SCH,1.74%of pregnant women might be misdiagnosed with SCH in early pregnancy,3.34%in mid-pregnancy,and 6.97%in late pregnancy;if the upper limit of TSH reference value provided by Dia Sorin kit was used for the diagnosis of SCH,2.36%of pregnant women might be misdiagnosed with SCH in early pregnancy.If the upper limit of TSH reference value provided by Dia Sorin kit is used for the diagnosis of SCH,2.36%of pregnant women may be missed in early pregnancy,1.66%in middle pregnancy,and 1.47%in late pregnancy;if the upper limit of TSH reference value recommended by the 2019 Chinese guidelines is used for the diagnosis of SCH,1.76%of pregnant women may be missed in early pregnancy and 2.54%in middle pregnancy.In late pregnancy,1.47%of pregnant women may be misdiagnosed.Conclusion(s):1.this study initially established the region of Qujing,mainly the region of specific thyroid function reference values for women in pregnancy in our hospital.2.the existence of variations in thyroid hormone levels among pregnancy periods in women during pregnancy.3.the diagnostic criteria recommended by 2017 ATA,Dia Sorin kit or 2019Chinese guidelines will expand the rate of misdiagnosis or missed diagnosis of SCH in women in early and middle and late pregnancy in Qujing area,and the region specific serum thyroid hormone reference value area should be used as the reference value area for women during pregnancy.