title: A comparison of prevaginal and postvaginal manipulation fetal fibronectin.
abstract: BACKGROUND
  Fetal fibronectin (fFN) is used as a biomarker for preterm delivery. Currently, its use is discouraged if there has been vaginal manipulation in the previous 24 hours.
  
  
  OBJECTIVE
  Our objective is to determine if there are differences between fFN results before and after vaginal manipulation in the form of sterile vaginal exam or transvaginal ultrasound.
  
  
  METHODS
  This was a prospective observational cohort study at a single center of women between 22-33 6/7 weeks at risk for preterm delivery due to: (1) a history of preterm delivery, short cervix, or multifetal gestation; or (2) symptoms of preterm labor. We excluded women with vaginal bleeding or infection, placenta previa, ruptured membranes, cervical dilation >3 cm, or any form of vaginal manipulation in the previous 24 hours. Specimen A was collected prior to planned vaginal exam or transvaginal ultrasound and specimen B was collected within 4 hours. The agreement between specimens A and B was assessed using descriptive statistics. Test characteristics of specimens A and B using the outcome of preterm delivery (<37 weeks) were calculated.
  
  
  RESULTS
  In all, 310 specimen pairs from 237 women were collected. Specimen A was positive in 37 (12%) instances and negative in 273 (88%) while specimen B was positive in 39 (13%) and negative in 271 (87%). There were discordant results in 26 specimen pairs. Of these, 14 (5%) negative specimen A results subsequently became positive for specimen B, and 12 (32%) positive specimen A results became negative for specimen B. Overall, there was a 92% agreement between specimens A and B (confidence interval, 88-94%). The specificity of specimens A and B for preterm birth was 90% vs 89%, respectively, with a negative predictive value of 87% for both. The false-negative rate was 12.8% for specimen A and 13.3% for specimen B.
  
  
  CONCLUSIONS
  There is a moderately high degree of agreement between prevaginal and postvaginal manipulation fFN results. Their test characteristics for evaluating preterm birth are similar with strong specificity and negative predictive values, and their false-negative rates are not clinically different. Consideration should be made to the utilization of postvaginal manipulation fFN when a prevaginal manipulation specimen is not available.
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY. Electronic address: amy.turitz@gmail.com.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Turitz
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Ackerman
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY.
authors.forename: Denise L
authors.initials: DL
authors.lastname: Johnson
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY.
authors.forename: Tracy C
authors.initials: TC
authors.lastname: Bank
authors.affiliation: Department of Biostatistics, Columbia University, New York, NY.
authors.forename: Jimmy K
authors.initials: JK
authors.lastname: Duong
authors.affiliation: Department of Biostatistics, Columbia University, New York, NY.
authors.forename: Shing M
authors.initials: SM
authors.lastname: Lee
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Gyamfi-Bannerman
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D015331:Cohort Studies; D005260:Female; D005333:Fetus / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism*; D058869:Gynecological Examination; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D047928:Premature Birth / Q000175:diagnosis; D012680:Sensitivity and Specificity; D014463:Ultrasonography; D014621:Vagina / Q000000981:diagnostic imaging* / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D005353:Fibronectins
keywords: fetal fibronectin; preterm birth; sterile vaginal exam; transvaginal ultrasound; vaginal manipulation