A-406 Lactate at the SGH Emergency Department – can Point-of-Care Test Results be Interpretated Interchangeably with Central Laboratory Test Results?

Abstract Backgrounds The diagnostic utility of lactate measurement at the emergency department includes functioning as a marker for resuscitation, identifying patients with occult hypoperfusion and providing prognostic information. For prompt emergency care triage, rapid availability of lactate results through point-of-care testing (POCT) has becoming more popular and widely used. At Singapore General Hospital, the Emergency Department (ED) has available two POCT analyzers for lactate measurement, the portable handheld i-STAT Alinity system and benchtop Cobas b221 blood gas analyzer; while the central Clinical Biochemistry Laboratory is measuring lactate, plasma on Beckman Coulter AU5800 chemistry analyzer. The aim of this study is to evaluate the correlation of lactate measurement on POCT analyzers against the central laboratory analyzer for potential interchangeable use of results reported from these analyzers. Methods A total of 91 patients’ samples were used for this study. Leftover arterial blood gas samples (in heparinized syringes) and plasma samples (spun down in sodium fluoride tubes) collected at the same time from patients admitted to Emergency Department were identified and tested within one hour of arrival in the laboratory. The arterial blood gas samples were promptly measured for lactate on both i-STAT Alinity and Cobas b221 blood gas analyzers, while the plasma samples were measured on Beckman AU5800 analyzer. Method comparison between POCT analyzers and the central laboratory analyzer was performed using Analyze-It v6.15 software. Results With reference to RCPA analytical performance specification (APS) for POCT lactate (= 4.0 mmol/L: ± 0.5 mmol/L, 4.0 mmol/L: ± 12%), Altman-Bland analysis showed poor agreement between arterial blood gas lactate measured on POCT Cobas b221 analyzer against central laboratory Beckman Coulter AU5800 chemistry analyser (= 4.0 mmol/L: +0.53 mmol/L (95%CI of 0.43 mmol/L to 0.62 mmol/L) and 4.0 mmol/L: +11.57% (95%CI of 8.11% to 15.04%)). In contrast, comparison statistics between arterial blood gas lactate on POCT Abbott iSTAT Alinity with both POCT Cobas b221 analyzer and Beckman Coulter AU5800 chemistry analyser (= 4.0 mmol/L: +0.27 mmol/L (95%CI of 0.17 mmol/L to 0.37 mmol/L) and -0.28mmol/L (95%CI of -0.31 mmol/L to 0.22 mmol/L), 4.0 mmol/L: +0.02% (95%CI of -3.14% to 3.19% and -11.56% (-21.93% to -1.20%), respectively) fell within the APS . Conclusion The observed bias between lactate measurements on the three analytical platforms may be attributed to differences in sample types and methodologies. The laboratory should communicate to ED clinicians that lactate results reported on different analytical methods and sample types should not be used interchangeably.