Development, Validation, and Diagnostic Accuracy of the Fetal Lack of Responsiveness Scale for Diagnosis of Severe Perinatal Hypoxia.

Background: There are limitations to predicting perinatal asphyxia, as current tools rely almost entirely on fetal cardiotocography (CTG). The fetal lack of responsiveness scale (FLORS) is a new diagnostic alternative based on the physiological phenomena associated with fetal hypoxia. Objectives: The objective of this study was to develop, validate, and assess the diagnostic accuracy of the FLORS for predicting severe perinatal hypoxia (SPH). Study Design: A two-phase retrospective observational cross-sectional analytical study was conducted. Phase 1 involved the formulation and retrospective validation of the FLORS. A total of 366 fetal CTG records were evaluated twice by seven readers. Phase 2 was a collaborative, retrospective, multicenter diagnostic test study that included 37 SPH and 366 non-SPH cases. Results: Phase 1: A numeric, physiology-based scale was developed and refined based on expert opinions. The median time to apply the scale per reading was 38 s. Cronbach's alpha, which is a reliability measure, was significant (p = 0.784). The kappa index for test-retest agreement was moderate to reasonable, with a median value of 0.642. For interobserver agreement, the kappa index per variable was as follows: baseline, 0.669; accelerations, 0.658; variability, 0.467; late/variable decelerations, 0.638; slow response decelerations, 0.617; and trend to change, 0.423. Phase 2, including 37 SPH and 366 non-SPH cases, showed a sensitivity of 62.2% and specificity of 75.4% for the 2-point score, whereas the 3-point score had a sensitivity of 35.1% and specificity of 89.9%. The area under the curve (AUC) was significant at 0.73 (CI 0.645-0.818). Conclusions: FLORS demonstrated significant internal consistency and observer agreement, with a promising sensitivity-specificity balance and significant AUC. Further research is needed to assess its impact on perinatal hypoxia and cesarean delivery.