Analytical validation of microdialysis analyzer for monitoring glucose, lactate and pyruvate in cerebral microdialysates

Background: Cerebral microdialysis is a valuable tool for neurochemical monitoring of acute brain injury. We performed an independent analytical validation of glucose, lactate and pyruvate methods on the new ISCUS(flex) new analyzer developed by CMA Microdialysis.

Methods: Evaluation of analytical parameters included limit of detection, limit of quantification, linearity, intra- and inter-assay imprecision expressed as the coefficient of variation (CV), recovery, inter-sample and inter-reagent contamination, drug and bilirubin interferences, sample stability, method comparison.

Results: Linearity ranges were 0.1-25 mmol/L, 0.2-12 mmol/L and 19-1500 μmol/L for glucose, lactate and pyruvate respectively. For critical threshold, intra- and inter-assay CVs were 3.1/4.5% for glucose (1 mmol/L), 3.5/4% for lactate (4 mmol/L) and 3.3/4.3% for pyruvate (100 μmol/L). Inter-assay CVs for lactate/pyruvate (LPR) and lactate/glucose (LGR) ratios were 5.9% and 6.0% respectively. For glucose, lactate, pyruvate, LPR and LGR, the reference change values (RCV) were 20%, 26%, 20%, 27% and 28% respectively. Practically, variations below 27% between two successive LPR values could not be interpreted as significant.

Conclusion: These data prove that ISCUS(flex) has the qualities required for clinical application in neuro-intensive care. Correct clinical interpretation of data need the implementation of a strict quality control program and strong cooperation between clinicians and biologists.