Clinical evaluation of Statstrip® Lactate for use in fetal scalp blood sampling.

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.

Inter- and intra-observer agreement of non-reassuring cardiotocography analysis and subsequent clinical management.

OBJECTIVE: To quantify inter- and intra-observer agreement of non-reassuring intrapartum cardiotocography (CTG) patterns and subsequent clinical management. DESIGN: Methodological study. SETTING: University Medical Center. POPULATION: CTG patterns of 79 women beyond 37 weeks of gestation with a singleton fetus in vertex position in first stage of labor in whom fetal blood sampling (FBS) had been performed. METHODS: Nine observers assessed CTG patterns, which were formerly clinically classified as non-reassuring and indicative for FBS, according to the guidelines of the International Federation of Gynecology and Obstetrics modified for ST analysis. They also proposed clinical management strategies without and with insight into clinical parameters. Weighted kappa values (κw ) and proportions of agreement (Pa ) were calculated. MAIN OUTCOME MEASURES: Agreement on CTG classification and clinical management. RESULTS: Inter-observer agreement on CTG classification and on clinical management were poor for most observer categories (κw range 0.31-0.50 and 0.20-0.45, respectively). Observers agreed best on abnormal CTG patterns (Pa range 0.28-0.36) and on the clinical management option "continue monitoring" (Pa range 0.32-0.40). Intra-observer agreement was fair to good for most observers (κw 0.33-0.70). Insight into clinical parameters resulted in similar inter- and intra-observer agreement. CONCLUSIONS: There was poor inter-observer agreement and fair to good intra-observer agreement on classification and clinical management of intrapartum CTG patterns, which had been classified as non-reassuring and indicative for FBS during birth.

Comparison of two point-of-care testing (POCT) devices for fetal lactate during labor.

BACKGROUND: Point-of-care testing (POCT) of fetal scalp blood lactate is used as an alternative for pH analysis. Lactate measurements have not been standardized and values vary with each device used. The aim of this study was to evaluate the performance of two POCT lactate meters for intrapartum use. METHODS: Analytical performance of StatStrip Lactate (Nova Biomedical) and Lactate Pro (Arkray) was evaluated using CLSI EP10. Both POCT meters were compared with our lactate reference method (RapidLab 860; Siemens Healthcare Diagnostics) using fetal scalp and neonatal cord blood. Deming regression analysis was performed. RESULTS: StatStrip Lactate coefficients of variation (CVs) were 5.1%, 5.0% and 2.6% at 0.9, 7.5 and 14.1 mmol/L lactate, respectively. CVs for Lactate Pro were 10.7%, 5.2% and 5.7% at 1.7, 4.1 and 6.4 mmol/L lactate, respectively. Consecutive lactate measurements in 37 fetal scalp and 122 cord blood samples revealed different test characteristics for the two POCT devices. In fetal scalp blood: StatStrip Lactate=1.13*RapidLab-0.39 (R(2)=0.907) and Lactate Pro=0.95*RapidLab-0.03 (R(2)=0.823). In cord artery blood: StatStrip Lactate=1.08*RapidLab-0.09 (R(2)=0.810) and Lactate Pro=0.72*RapidLab+0.59 (R(2)=0.807). CONCLUSIONS: Overall performance of both Lactate Pro and StatStrip Lactate was good, with StatStrip Lactate having smallest CVs and closest correlation to our reference method. Both StatStrip Lactate and Lactate Pro can be used as a lactate POCT device for obstetric use.

Scalp blood lactate for intra-partum assessment of fetal metabolic acidosis.

OBJECTIVE: To study to what extent the fetal scalp blood lactate concentration during labor correlates with fetal scalp pH and base deficit, and metabolic acidosis at birth, and to suggest lactate cut-off values to serve as indicators for either reassurance or immediate intervention. DESIGN: A retrospective observational study. SETTING: Labor ward at a university medical center. SAMPLE: Fetal scalp and cord blood samples with acid-base and lactate values from 486 singleton pregnancies beyond 34 weeks' gestation. METHODS: The relation between lactate, pH and base deficit (BD) in fetal scalp blood was tested by Spearman's rho correlation coefficient. Lactate cut-off values indicating either reassuring fetal status or immediate intervention were estimated using percentile distribution and compared with pH and BD. MAIN OUTCOME MEASURES: Metabolic acidosis, defined as umbilical cord artery pH below 7.05 and BD calculated for the blood compartment above 12 mmol/l. RESULTS: After 127 (21%) exclusions, 486 cases were available for analysis. Fetal lactate values increased with evolving metabolic acidosis. Lactate concentration correlated with both pH (r=-0.50, p<0.01) and BD (r=0.48, p<0.01). Lactate <5.4 mmol/l indicated reassuring fetal status, whereas lactate ≥6.6 mmol/l indicated metabolic acidosis. Fetal lactate correlated better with either the absence or presence of metabolic acidosis at birth than did fetal pH and BD. CONCLUSIONS: In the case of a non-reassuring fetal heart rate, fetal scalp blood lactate provides more accurate information on fetal acid-base status than does pH and/or BD.