Comparison of protein S functional and antigenic assays in normal pregnancy

• Published in: American journal of obstetrics and gynecology 1996-09, Vol.175 (3), p.657-660
• Main Authors: LEFKOWITZ, J. B, CLARKE, S. H, BARBOUR, L. A
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Antigens - blood; Biological and medical sciences; Complement Inactivator Proteins; Cross-Sectional Studies; Factor V - analysis; Factor VIII - analysis; Female; functional testing; Glycoproteins; Gynecology. Andrology. Obstetrics; Humans; Management. Prenatal diagnosis; Medical sciences; Partial Thromboplastin Time; Pregnancy; Pregnancy. Fetus. Placenta; Protein S; Protein S - analysis; Protein S - immunology; Protein S - physiology; Protein S Deficiency - blood; Protein S Deficiency - diagnosis; Receptors, Complement - blood; Reference Values; Time Factors
• ISSN: 0002-9378; 1097-6868
• DOI: 10.1053/ob.1996.v175.a73866

OBJECTIVE: Our purpose was to determine the effect of pregnancy on the protein S functional assay (clot based), which is used to screen for all subtypes of protein S deficiency states, and to compare its behavior in pregnancy with antigenic assays. STUDY DESIGN: This was a cross-sectional study of 37 normal pregnant women without thromboembolic risks who were tested by both functional and antigenic protein S assays during the first, second, and third trimesters. RESULTS: Mean protein S functional levels decline strikingly from the first to the third trimester, all 10 third-trimester patients had functional protein S levels well below the lower limit of the reference range. In contrast, only 3 of 10 third-trimester and none of the second-trimester patients had free protein S antigenic levels below the reference range. CONCLUSIONS: The protein S functional assay should not be used in pregnancy to screen for the subtypes of protein S deficiency; misdiagnosis and inappropriate treatment could result. (Am J Obstet Gynecol 1996;175:657-60.)