Plasma lactate measurement as an example of encountered gaps between routine clinical laboratory processes and manufactures’ sample-handling instructions

Objectives: Deviation from manufacturers’ pre-analytical sample handling recommendations necessitates extensive validation studies. This report uses plasma lactate testing, where a recommended 15 min room temperature sample handling limit cannot be met by the clinical laboratory, as an example for studies to bridge the gap with practice. Design and Methods: Triplicate blood samples were collected from patients (n = 51) with lactate requests by clinicians and from normal volunteers (n = 50). One tube was transported on ice (4 °C), the others were maintained at room temperature (23 °C). Tubes stored at 4 °C were processed at 30 min from collection. Tubes stored at 23 °C were processed at 15 and at 30 min from collection. Lactate levels were measured using Roche Diagnostics Cobas 6000® analyzer. Results: Lactate levels in normal subjects ranged from 0.6 to 3.1 mmol/L (median 1.1). Patient lactate levels ranged from 0.8 to 26.3 mmol/L (median 2.2). Bias in lactate levels following extended storage of samples from both normal subjects and patients ranged from − 1.3 to2.2 and from − 1.0–1.0 mmol/L when stored for 30 min at 23 °C or at 4 °C, respectively. The bias between lactate levels at 30 min at 23 °C and 4 °C was − 1.2 to − 0.5 mmol/L for both populations. Although the bias was not statistically significant for all variables, a clinically significant (>0.2 mmol/L) bias was observed in 28% of normal and 7.0% of patient samples. Conclusion: Extending the pre-analytical time to 30 min at 23 °C did not significantly impact clinical utility of lactate measurement in our patient population.