Diagnostic Accuracy of the FIGO and the 5-Tier Fetal Heart Rate Classification Systems in the Detection of Neonatal Acidemia

Abstract

<b>Objective</b> The objective of this study was to determine ability to detect neonatal acidemia and interobserver agreement with the FIGO 3-tier and 5-tier fetal heart rate (FHR) classification systems. <b>Design</b> This was a case-control study. <b>Setting</b> This study was set at the University Medical Center. <b>Population</b> A total of 202 FHR tracings of 102 women who delivered an acidemic fetus (umbilical arterial cord gas pH ≤ 7.10 and BE < - 8) and 100 who delivered a nonacidemic fetus (umbilical arterial cord gas pH > 7.10) were assessed. A subanalysis was performed for those fetuses who suffered severe metabolic acidemia (pH ≤ 7.0 and BE < - 12). <b>Methods</b> Two reviewers blind to clinical and outcome data classified tracings according to the new 3-tier system proposed by the FIGO and the 5-tier system proposed by Parer and Ikeda. <b>Main Outcome Measures</b> Sensitivity and specificity for detecting neonatal acidemia and interobserver agreement in classifying FHR tracings into categories of both systems were studied. <b>Results</b> The 3-tier system showed a greater sensitivity and lower specificity to detect neonatal acidemia (43.6% sensitivity, 82.5% specificity) and severe metabolic acidemia (71.4% sensitivity, 74.0% specificity) compared with the 5-tier system (36.3% sensitivity, 88% specificity and 61.9% sensitivity, 80.1% specificity, respectively). Both systems were compared by area under the receiver-operating characteristic curve, with comparable predictive ability for detecting neonatal acidemia (FIGO-area under the curve [AUC]: 0.63 [95% confidence interval [CI]: 0.57-0.68] and Parer-AUC: 0.62 [95% CI: 0.56-0.67]). Interobserver agreement was moderate for both systems, but performance at each specific category showed a better agreement for the 5-tier system identifying a pathological tracing (orange or red, κ: 0.625 vs. pathological category, κ: 0.538). <b>Conclusion</b> Both systems presented a comparable ability to predict neonatal acidemia, although the 5-tier system showed a better interobserver agreement identifying pathological tracings.