title: False positive rate of serum markers for Down syndrome screening: does transportation have any effect?
abstract: OBJECTIVE
  To determine the false positive rate of serum markers for Down syndrome screening caused by transportation by analyzing samples sent from different hospitals at various distances.
  
  
  METHODS
  The database of serum markers between March 2008 and August 2010 was retrieved from Maternal-Fetal the Medicine unit, Department of Obstetrics and Gynecology, Faculty of Medicine, Chiang Mai University. The tests were performed using Delfia Xpress system. The cut off value for positive test result was 1 in 250.
  
  
  RESULTS
  Two thousand six hundred thirty one samples from hospitals located at various distances ranging from 0 to 449 km were assessed. The overall positive results were 6.1%, ranging from 5.6% among the hospitals near the laboratory to 15.4% among the hospitals far away from the laboratory (p-value < 0.001). The samples from the remote hospitals had significantly higher levels of free beta hCG than those from nearby hospitals (p-value = 0.003).
  
  
  CONCLUSIONS
  The samples transported from the hospitals far from the laboratory need better storage and shipping procedure to avoid high false positive rate, which leads to unnecessary invasive prenatal diagnosis procedure.
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
authors.forename: Supatra
authors.initials: S
authors.lastname: Sirichotiyakul
authors.forename: Suchaya
authors.initials: S
authors.lastname: Luewan
authors.forename: Rattanaporn
authors.initials: R
authors.lastname: Sekararith
authors.forename: Theera
authors.initials: T
authors.lastname: Tongsong
mesh_terms: D015415:Biomarkers / Q000097:blood*; D001800:Blood Specimen Collection / Q000592:standards; D004314:Down Syndrome / Q000175:diagnosis*; D005189:False Positive Reactions; D006801:Humans; D012189:Retrospective Studies; D014186:Transportation
chemical_list: D015415:Biomarkers