Establishment of Trimester-Specific Reference Intervals of Serum TSH & fT4 in a Pregnant Indian Population at North Kolkata.
Reference intervals (RIs) of serum thyroid stimulating hormone (TSH) and free thyroxine (fT4) were determined in 402 healthy pregnant women by enzyme-linked immunosorbent assay (ELISA) technique after partitioning them into three trimesters. The reference population was chosen from a study population of 610 pregnant females by applying strict inclusion and exclusion criteria. The assays were done using proper quality control measures. RIs were calculated from the central 95 % of the distribution of TSH and fT4 values located between the lower reference limit of 2.5 percentile and upper reference limit of 97.5 percentile value 0.90 confidence intervals for the upper and lower reference limits were also determined. The reference intervals for TSH were 0.25-3.35 μIU/ml for the first trimester; 0.78-4.96 μIU/ml for the second trimester and 0.89-4.6 μIU/ml for the third trimester. Similarly, the reference intervals for fT4 for first, second and third trimesters were 0.64-2.0, 0.53-2.12 and 0.64-1.98 ng/dl respectively. The values thus obtained varied from those provided by the kit literature. In comparison to our derived reference intervals, the reference data from kit manufacturer under-diagnosed both subclinical hypo- and hyper-thyroidism within our pregnant reference population.
Department of Biochemistry, R.G.Kar Medical College and Hospital, Kolkata, West Bengal India ; 23/2/1 D.P.P Road, P.O Naktala, Kolkata, 700047 West Bengal India.
Rituparna
R
Maji
Department of Biochemistry, R.G.Kar Medical College and Hospital, Kolkata, West Bengal India.
Sukla
S
Nath
Department of Community Medicine, R.G.Kar Medical College and Hospital, Kolkata, West Bengal India.
Surajit
S
Lahiri
Department of Biochemistry, R.G.Kar Medical College and Hospital, Kolkata, West Bengal India.
Mita
M
Saha Das
Department of Gynaecology and Obstetrics, R.G.Kar Medical College and Hospital, Kolkata, West Bengal India.
Ajit Ranjan
AR
Bhattacharyya
Department of Biochemistry, R.G.Kar Medical College and Hospital, Kolkata, West Bengal India.
Harendra Nath
HN
Das
ELISA; Pregnancy; Reference interval; Reference range; Thyroid hormones; Trimester-specific