Validation and proposal of a clinical intervention cutoff in fetal scalp blood for the point-of care-lactate meter StatStrip®2

Abstract

Introduction: This multicenter, prospective observational study aimed to evaluate the performance of the StatStrip® Lactate 2 (Nova Biomedical, Waltham, US) point-of-care device for fetal blood lactate measurement and to determine the corresponding lactate value equivalent to the established intervention cutoff used with the outgoing StatStrip® Lactate device. Material and Methods: The study was conducted from August 2024 to February 2025 at two maternity clinics in Sweden and one in Denmark. It included women with singleton pregnancies (≥35 + 0 weeks) undergoing fetal blood sampling due to non-reassuring intrapartal fetal heart rate patterns during labor. Fetal scalp blood sampling (FBS) lactate concentrations were measured using both StatStrip® Lactate and StatStrip® Lactate2. The first StatStrip® Lactate measurement guided clinical decisions, while subsequent StatStrip® Lactate2 measurements were recorded for validation and establishment of a conversion equation by linear regression. Additionally, arterial and venous umbilical cord blood samples were analyzed by both ABL 800 (Radiometer, Denmark) and StatStrip® Lactate2 for validation. Results: Blood samples from 349 fetuses were included, with 549 parallel FBS lactate samples. StatStrip® Lactate2 concentrations correlated with StatStrip® Lactate (r = 0.94;p ≤ 0.001). A conversion equation was retrieved: StatStrip® Lactate2 = (1.4 × StatStrip® Lactate) − 0.28. From 37 paired umbilical cord blood samples, the correlation between lactate concentrations by StatStrip® Lactate2 and ABL800 was r = 0.99 (p ≤ 0.001) in arterial blood and r = 0.98 (p ≤ 0.001) in venous blood. Mean coefficients of variation for lactate concentrations >3.0 mmol/L were 8.2% in fetal scalp blood and 3.8% in umbilical cord blood. Conclusions: A fetal blood lactate concentration ≥7.0 mmol/L measured by StatStrip®Lactate2 corresponds to the established intervention cutoff lactate value ≥5.2 mmol/L measured by StatStrip®Lactate. Precision was acceptable but may be improved by using the mean of two measurements, particularly when the first result falls between 6.0 and 8.0 mmol/L. We also recommend ensuring the correct sampling techniques to minimize preanalytical variation.