Comparison of venous lactate values on blood gas analyser versus laboratory autoanalyser: A preliminary study

Background & objectives Lactate can be estimated by point-of-care testing (POCT) devices such as blood gas analysers (BGA) as well as central lab autoanalysers (AA); both have their advantages. Studies have compared lactate and electrolyte values on arterial blood; none used venous samples which are preferred in children. We planned to compare venous lactate by BGA and AA in children admitted to Paediatric Intensive Care Unit (PICU). Methods Fifty children aged one month to 18 yr admitted in PICU were included in the study after parental consent. Paired venous samples were collected in heparinised syringes for BGA, in fluoride containing vacutainers for AA and were analysed immediately. Results Lactate levels were assessed in 29 male and 21 female children [Median age: 4 yr interquartile range (IQR)=1-10)]. AA reported higher lactate levels but mean difference between two methods (0.34±1.56 mmol/L) was not statistically significant (P= 0.062). The methods showed statistically significant correlation [95% confidence interval (CI), Spearman correlation coefficient (rs)=0.816, P=<0.001]. Bland Altman plot showed 95 per cent of paired values had differences which was within limits of agreement (-2.71, +3.39); differences were more variable above 2 mmol/L. Both devices classified multiple samples into different clinically significant ranges. Interpretation & conclusion Venous lactate by BGA and AA was found comparable, but critical values requiring clinical intervention were not reported similarly by both analysers. Variability between them was higher at higher venous lactate levels (>2 mmol/L) which represent critically ill children. Use of the same analyser, either BGA or AA, is therefore recommended for monitoring.