Introduction: Point-of-care testing of fetal scalp blood lactate is used as an alternative to pH analysis in fetal scalp blood sampling (FBS) during labor. Lactate measurements are not standardized and values vary with each device used. The aim of this study was to evaluate StatStrip® Lactate (SSL) in the clinical setting in comparison with lactate (RLL) and pH (RLpH) using RapidLab® .
Material and methods: We obtained 323 FBS samples from 139 women. Parallel sampling of SSL and RLL/RLpH was performed in 247 samples. Outcome measures were the agreement and discrepancy rates between SSL, RLL and RLpH and the failure rate of all three methods. We constructed a Bland-Altman graph to assess the variability between the measurements across the range of values. The discrepancy rates between methods were compared using previously established cut-off values for SSL indicating reassurance (<5.7 mmol/L) and immediate delivery (>7.0 mmol/L) with those for RLpH (<7.20 and >7.25).
Results: SSL showed excellent agreement with RLL (R2 = 0.742) and poor agreement with RLpH (R2 = 0.204). Failure rates for SSL, RLL and RLpH were 7, 43 and 23%, respectively. Using the cut-off values for reassurance and immediate delivery, the discrepancy rates between SSL and RLpH were 14 and 5%, respectively.
Conclusions: SSL is a reliable test to measure lactate in FBS with a low failure rate. As there are discrepancies between SSL and RLpH, and the cut-off values have not yet been evaluated prospectively regarding intervention rates and neonatal outcome, we recommend using SSL in addition to pH in FBS.
Keywords: Fetal scalp blood sampling; cardiotocography; fetal distress; lactate; point-of-care-testing.
© 2016 Nordic Federation of Societies of Obstetrics and Gynecology.