title: [Free protein S (PS) in normal pregnancy: a comparison between two analytical methods].
abstract: BACKGROUND
  Pregnancy is a physiological hypercoagulable state with an increased incidence of thromboembolic phenomena. There is an increase in the concentrations of most clotting factors, a decrease in concentration of some of the natural anticoagulants and reduced fibrinolytic activity. Changes in PS levels have also been reported.
  
  
  OBJECTIVE
  To establish referral range values of functional PS and free PS antigen, during the second (2nd T) and third trimester (3rd T) of normal gestation.
  
  
  METHODS
  Forty one normal pregnant women were included in our study, 20 during the 2nd T (22-24 weeks) and 21 during the 3rd T (29-38 weeks). Functional PS was measured by a clot based test and free PS antigen by ELISA.
  
  
  RESULTS
  Free PS Antigen was 65.8+/-18.3% during the 2nd T and 62.3+/-16.5% during the 3rd T. The figures for normal controls were 106+/-6.5%. Functional PS was 43.8+/-13.3 and 25.9+/-14.6% during the 2nd T and 3rd T, respectively. The figures for normal controls were 97+/-24% (p <0.001 compared with pregnant women). Free PS antigen did not change from the 2nd to the 3rd T (p=NS), however functional PS fell significantly from the 2nd to the 3rd T (p <0.001) and was significantly lower than free PS antigen in both trimesters (p <0.001).
  
  
  CONCLUSIONS
  Pregnancy is associated to a decrease in PS. This abnormality is more pronounced for functional PS than free PS antigen and functional PS falls progressively during pregnancy. These assays should not be used to screen for PS deficiency during pregnancy because they could lead to a misdiagnosis.
authors.affiliation: Laboratorio de Hematología, Clínica Alemana, Santiago, Chile. pfardella123@msn.com
authors.forename: Patricia
authors.initials: P
authors.lastname: Fardella
authors.forename: Mauro
authors.initials: M
authors.lastname: Parra
authors.forename: Guillermo
authors.initials: G
authors.lastname: Conte
authors.forename: Claudio
authors.initials: C
authors.lastname: Flores
authors.forename: Hernán
authors.initials: H
authors.lastname: Muñoz
authors.forename: Lilian
authors.initials: L
authors.lastname: Soto
authors.forename: Marianela
authors.initials: M
authors.lastname: Cuneo
authors.forename: Carmen
authors.initials: C
authors.lastname: Mallea
authors.forename: María Beatriz
authors.initials: MB
authors.lastname: Retamales
authors.forename: Sofía
authors.initials: S
authors.lastname: Peña
authors.forename: Constanza
authors.initials: C
authors.lastname: Ojeda
mesh_terms: D000293:Adolescent; D000328:Adult; D001780:Blood Coagulation Tests; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000592:standards; D005260:Female; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second / Q000097:blood*; D011263:Pregnancy Trimester, Third / Q000097:blood*; D011446:Prospective Studies; D017293:Protein S / Q000032:analysis*; D018455:Protein S Deficiency / Q000378:metabolism; D012016:Reference Values
chemical_list: D017293:Protein S