Suitability of POC lactate methods for fetal and perinatal lactate testing: considerations for accuracy, specificity and decision making criteria.

BACKGROUND

Point of care (POC) testing for fetal scalp blood lactate is a more user friendly and more successful approach compared to scalp pH for intrapartum fetal monitoring. The aim of this study was to assess the analytical specificity and clinical reliability of three POC lactate methods.

METHODS

The analytical performance of three POC lactate methods was compared to Cobas 6000 (Roche Diagnostics) laboratory reference method: Lactate Pro from Arkray, GEM 4000 from Instrumentation Laboratory and StatStrip Lactate from Nova Biomedical. The clinical performance and influences on accuracy and decision making criteria for the three POC methods was assessed with umbilical cord samples and compared to the laboratory reference method. The influence of varying ranges of hemoglobin, pH and partial oxygen pressure (pO(2)) on the accuracy of results was assessed.

RESULTS

Although all three POC methods showed good correlation with the reference method for the umbilical cord sample population (r=0.989, 0.973 and 0.980, respectively), Lactate Pro and Gem 4000 showed a significant negative bias compared to the reference method. The degree of bias meant a significant readjustment of decision making criteria was required for fetal lactate use. The accuracy of the Lactate Pro results was affected by hemoglobin and to a lesser extent pH.

CONCLUSIONS

The three electrochemical POC devices can measure fetal lactate reliably. StatStrip Lactate showed a closer correlation and concordance to our laboratory reference method. The results of this study indicate the requirement for predetermining the reliability of POC lactate methods before use present in fetal and perinatal settings.