title: Diagnostic accuracy of fetal scalp lactate for intrapartum acidosis compared with scalp pH.
abstract: OBJECTIVE
  To determine the diagnostic accuracy of fetal scalp lactate sampling (FSLS) and to establish an optimal cut-off value for intrapartum acidosis compared with fetal scalp pH.
  
  
  METHODS
  A 20-month retrospective cohort study was conducted of all neonates delivered in our institution for whom fetal scalp blood sampling (FSBS) was performed, matching their intrapartum gasometry to their cord gasometry at delivery (n=243). The time taken from the performance of scalp blood sampling to arterial umbilical cord gas acquisition was 45 min at most. Five arterial cord gasometry patterns were set for assessing the predictive ability of both techniques. Subsequent obstetric management for a pathological value was analysed considering the use of both techniques.
  
  
  RESULTS
  The optimal cut-off value for FSLS was 4.8 mmol/L: this value has 100% sensitivity and 63% specificity for umbilical arterial cord gas pH≤7.0 and base deficit (BD)≥12 detection, and 100% sensitivity and 64% specificity for umbilical arterial cord gas pH≤7.10 and BD≥12 detection, with a false negative rate of <1.3%, improving fetal scalp pH performance. FSLS showed the best area under the curve (AUC) of 0.86 and 0.84 for both arterial cord gasometry patterns, respectively. Expedite birth following lactate criteria would have been the same as following pH criteria (92 obstetric interventions) with no cases of missed metabolic acidosis. In the cohort, 19.8% of cases were discordant, but no cases of metabolic acidosis were in this group.
  
  
  CONCLUSIONS
  FSLS improves the detection of metabolic acidosis via fetal scalp pH with an optimal cut-off value of 4.8 mmol/L. FSLS can be used without increasing obstetrical interventions or missing metabolic acidosis.
authors.affiliation: Departamento de Obstetricia, Hospital Universitario Miguel Servet, P° Isabel la Católica, Zaragoza 50009.
authors.forename: Jara
authors.identifier: http://orcid.org/0000-0002-5869-4450
authors.initials: J
authors.lastname: Pascual Mancho
authors.affiliation: Departamento de Obstetricia, Hospital Universitario Miguel Servet, P° Isabel la Católica, Zaragoza 50009.
authors.forename: Sabina
authors.identifier: http://orcid.org/0000-0002-6767-9084
authors.initials: S
authors.lastname: Marti Gamboa
authors.affiliation: Departamento de Obstetricia, Hospital Universitario Miguel Servet, P° Isabel la Católica, Zaragoza 50009.
authors.forename: Olga
authors.identifier: http://orcid.org/0000-0003-3961-0458
authors.initials: O
authors.lastname: Redrado Gimenez
authors.affiliation: Departamento de Obstetricia, Hospital Universitario Miguel Servet, P° Isabel la Católica, Zaragoza 50009.
authors.forename: Raquel
authors.initials: R
authors.lastname: Crespo Esteras
authors.affiliation: Departamento de Obstetricia, Hospital Universitario Miguel Servet, P° Isabel la Católica, Zaragoza 50009.
authors.forename: Belen
authors.initials: B
authors.lastname: Rodriguez Solanilla
authors.affiliation: Departamento de Obstetricia, Hospital Universitario Miguel Servet, P° Isabel la Católica, Zaragoza 50009.
authors.forename: Sergio
authors.initials: S
authors.lastname: Castan Mateo
mesh_terms: D000140:Acidosis, Lactic / Q000097:blood* / Q000175:diagnosis*; D000328:Adult; D015331:Cohort Studies; D005189:False Positive Reactions; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D005323:Fetal Monitoring / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D011237:Predictive Value of Tests; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D012189:Retrospective Studies; D012535:Scalp / Q000098:blood supply / Q000378:metabolism*
chemical_list: D019344:Lactic Acid
keywords: Diagnostic test; fetal scalp sampling; intrapartum acidosis; lactate; pH; sensitivity; specificity