title: Population Reference Values and Prevalence Rates following Universal Screening for Subclinical Hypothyroidism during Pregnancy of an Afro-Caribbean Cohort.
abstract: BACKGROUND
  Subclinical hypothyroidism (SCH) has been reported to be associated with adverse pregnancy outcomes, however universal screening and treatment is controversial.
  
  
  OBJECTIVE
  Our objectives were to determine population-specific pregnancy reference values (R1) for serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) at 14 weeks' gestation, along with the prevalence of SCH and thyroid peroxidase antibody (TPOAb).
  
  
  METHODS
  This was a prospective hospital-based cohort study. 1,402 subjects were recruited. Blood samples were obtained from 769 singleton pregnancies due to default between recruitment and scheduled blood draw. The prevalence of SCH was determined using R1, the laboratory non-pregnant reference values (R2) and previously recommended pregnancy reference values (R3).
  
  
  RESULTS
  R1 for TSH and FT4 was 0.03-3.17 mU/l (mean ± SD, 1.1 ± 0.76) and 8.85-17.02 pmol/l (mean ± SD, 11.96 ± 2.06), respectively. The prevalence of SCH using reference values R1, R2 and R3 was 1.4% (11/769), 0.5% (4/769) and 1.9% (15/769). Prevalence was significantly greater using R3 when compared to R2 (p = 0.011). TPOAb prevalence was 2.6%. A significantly greater prevalence of TPOAb was found in subclinical hypothyroid subjects using all three reference values than in euthyroid subjects (∼25 vs. 2%, p < 0.05).
  
  
  CONCLUSIONS
  These reference values are the first to be reported for an Afro-Caribbean population. Our findings support the use of pregnancy-specific reference values in our population.
authors.affiliation: Department of Obstetrics and Gynaecology, Kingston, Jamaica.
authors.forename: Nadine
authors.initials: N
authors.lastname: Johnson
authors.affiliation: Department of Obstetrics and Gynaecology, Kingston, Jamaica.
authors.forename: Vikash
authors.initials: V
authors.lastname: Chatrani
authors.affiliation: Department of Obstetrics and Gynaecology, Kingston, Jamaica.
authors.forename: Anna-Kay
authors.initials: AK
authors.lastname: Taylor-Christmas
authors.affiliation: Department of Chemical Pathology, Kingston, Jamaica.
authors.forename: Eric
authors.initials: E
authors.lastname: Choo-Kang
authors.affiliation: Department of Microbiology, Kingston, Jamaica.
authors.forename: Monica
authors.initials: M
authors.lastname: Smikle
authors.affiliation: Department of Medicine, Kingston, Jamaica.
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Wright-Pascoe
authors.affiliation: Department of Medicine, Kingston, Jamaica.
authors.forename: Karen
authors.initials: K
authors.lastname: Phillips
authors.affiliation: Department of Tropical Metabolism Research Institute, University of the West Indies, Kingston, Jamaica.
authors.forename: Marvin
authors.initials: M
authors.lastname: Reid
keywords: Subclinical hypothyroidism; Universal screening