TOPLINE

Lactate and pH in fetal scalp blood samples (FBS) demonstrated a moderate inverse linear correlation, with lactate showing good diagnostic performance for identifying abnormal pH values. A lactate cutoff of ≥ 5.6 mmol/L demonstrated an optimal balance between sensitivity and specificity.

METHODOLOGY

• An observational prospective single-center study was conducted in the Netherlands over 8 months, analyzing 263 FBS collected from 192 women during labor.
• Women with singleton pregnancies at ≥ 32 weeks' gestation in cephalic presentation who had indications for FBS based on cardiotocography interpretation were included.
• Researchers measured both pH (using iSTAT) and lactate (using StatStrip Lactate 2) in each FBS, with clinical decisions based solely on pH results.
• The primary objective was to assess correlation between lactate and pH in FBS and establish an appropriate lactate cutoff value indicating fetal distress; secondary outcomes included sensitivity and specificity for identifying cases with low 5-minute Apgar scores and acidosis.
• Diagnostic performance of lactate was evaluated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curve, from which cutoff values were derived based on optimal balance between highest sensitivity and specificity.

TAKEAWAY

• Lactate and pH in FBS showed a moderate inverse linear correlation (r = −0.53), with lactate values ranging from 0.6-11.8 mmol/L and pH values ranging from 7.06-7.40.
• The AUC of the ROC curve was 0.88 (95% CI, 0.83-0.93), indicating good diagnostic performance of lactate to identify an abnormal pH (pH < 7.20 in FBS).
• A lactate cutoff value of ≥ 5.6 mmol/L demonstrated the most optimal balance between sensitivity (78.1%) and specificity (79.2%).

IN PRACTICE

"This study confirmed that the StatStrip Lactate 2 is a suitable alternative analyzer for measurement of lactate compared with measurement of pH with the iSTAT in FBS. Despite only a moderate correlation between lactate and pH, a lactate cutoff value of ≥5.6 mmol/L could be proposed for clinical decision making," the authors of the study wrote.

SOURCE

The study was led by Suzanne J. van Woudenberg, Department of Obstetrics and Gynecology in Utrecht, the Netherlands. It was published online on July 31 in Acta Obstetricia et Gynecologica Scandinavica.

LIMITATIONS

The failure rate of lactate measurement could not be properly assessed because pH sampling was prioritized over lactate sampling, potentially leading to falsely marked failures or missed samples. The study could not evaluate operative delivery rates using lactate measurement since clinical decisions were based solely on pH results. 

DISCLOSURES

No specific funding was reported for the study. The authors reported no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.