Comparison of the NICE 2014 versus the NICE 2017 guidelines in predicting cord blood analysis

Abstract

Cardiotocographic (CTG) monitoring is used to detect early signs of fetal hypoxia. However, CTG monitoring in labour, has not been shown to improve overall perinatal mortality nor cerebral palsy. In spite of the lack of evidence regarding its benefit, CTG monitoring is standard of care in many countries.

Numerous guidelines by various professional bodies, are available to assist one in the interpretation of cardiotocograph (CTG) traces. The National Institute for Health and Care Excellence (NICE) first published its guidelines on intrapartum care in 2007. These were revised in 2014 and again in 2017. There were various changes to the description of CTG features in the revised 2017 guideline. The aim of this study was to assess if these changes improve observer interpretation of CTGs by comparing the sensitivity and specificity of each version of the guideline, using the results of cord blood analysis as the standard for this study.

This was an observational study conducted at Rahima Moosa Mother and Child Hospital, a regional hospital in the City of Johannesburg, Gauteng province, South Africa. This hospital is part of the University of the Witwatersrand academic circuit.

There were 193 patient files collected for a previous study done by the co-supervisor. A total of 84 CTGs within 90 minutes of delivery, had accompanying cord blood analyses. These CTGs were assessed and categorized using the NICE 2014 and thereafter the NICE 2017 guidelines. The sensitivity and specificity for each guideline was then calculated.

The NICE 2014 guideline had a sensitivity of 11% (95% CI, 0.28-48.20), and specificity of 87% (95% CI, 76.8-93.4). The NICE 2017 guideline had a sensitivity of 22% (95% CI, 2.81- 60), and a specificity of 80% (95% CI, 69.2-88.4). A limitation of this study was that cord blood pH was used as the only standard. There was no clinical correlation with low Apgar scores or need for newborn resuscitation which could have improved the sensitivity of the CTGs.

In conclusion, the NICE 2014 and the NICE 2017 guidelines performed poorly as a tool for assessing suspicious and pathological traces as determined by the accepted standard for this study i.e cord blood pH. Ultimately, CTG monitoring in labour, has not been shown to improve overall perinatal mortality nor cerebral palsy.[1] A cord blood pH of 7.10 has been found to be significantly associated with neonatal mortality.[12]

The interpretation of baseline variability, when using either version of the guideline, often played a role in falsely assessing traces as suspicious and pathological which when compared to the accepted standard of cord blood pH, were otherwise normal.

Both versions of the guidelines had very poor sensitives compared with those calculated in other studies. Specificity calculations for both versions of the guideline fared better when compared with those calculated in other studies. There was a tendency to an improved specificity with the NICE 2014 version of the guideline when compared to the accepted standard of cord blood pH. The NICE 2014 guideline required a fetal bradycardia in addition to a prolonged deceleration to categorize a CTG as “ Need for Urgent Intervention”, thereby reducing its rate of false positive assessments. However, due to the very small sample size with very few poor outcomes and the wide 95% confidence intervals , a final conclusion of a better performance of the 2014 vs the 2017 guidelines, could not be made.