title: Reference intervals for common coagulation tests of preterm infants (CME).
abstract: BACKGROUND
  Fresh-frozen plasma (FFP) is sometimes administered to nonbleeding preterm neonates who are judged to be at risk for bleeding because they have abnormal coagulation tests. The benefits/risks of this practice are not well defined. One limitation to progress is lack of reference intervals for the common coagulation tests, thus limiting precision about whether coagulation tests are indeed abnormal.
  
  
  METHODS
  In a sequential observational study, fetal blood was drawn at preterm birth (≤ 34 weeks) from the umbilical vein near the placenta. Fibrinogen, prothrombin time, activated partial thromboplastin time, D-dimer, platelet (PLT) count, and mean PLT volume were measured. Reference intervals were constructed using 5th and 95th percentile values. Associations were then sought between abnormal coagulation values at birth and bleeding problems identified during the first week.
  
  
  RESULTS
  Coagulation tests were drawn at 175 preterm deliveries and the results were organized into reference intervals by gestational age. No abnormal coagulation value, either alone or in combination, predicted hemorrhage (intraventricular, gastrointestinal, or pulmonary) during the first week. However, fibrinogen exceeding the 95th percentile was associated with evidence of in utero infection/inflammation (correlations with elevated C-reactive protein, p<0.01, and elevated immature to total neutrophil ratio, p<0.001).
  
  
  CONCLUSIONS
  Abnormal coagulation values at preterm birth do not predict bleeding during the first week. This suggests to us that bleeding in the days after preterm birth is not generally the result of in utero coagulopathy. These findings bring into question the value of coagulation screening of nonbleeding preterm infants and prophylactic FFP administration to those with abnormal values.
authors.affiliation: Women and Newborns Clinical Program, Intermountain Healthcare, Salt Lake City, Utah; McKay-Dee Hospital Center, Ogden, Utah; Institute for Healthcare Delivery Research, Salt Lake City, Utah; Transfusion Medicine and Clinical Pathology Programs Intermountain Medical Center, Murray, Utah.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Christensen
authors.forename: Vickie L
authors.initials: VL
authors.lastname: Baer
authors.forename: Diane K
authors.initials: DK
authors.lastname: Lambert
authors.forename: Erick
authors.initials: E
authors.lastname: Henry
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Ilstrup
authors.forename: Sterling T
authors.initials: ST
authors.lastname: Bennett
mesh_terms: D001777:Blood Coagulation / Q000502:physiology; D001778:Blood Coagulation Disorders / Q000175:diagnosis; D001780:Blood Coagulation Tests / Q000379:methods*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D010314:Partial Thromboplastin Time; D010949:Plasma / Q000502:physiology; D011247:Pregnancy; D011517:Prothrombin Time; D012015:Reference Standards