Results from the external quality assessment for blood alcohol concentration analysis in Lombardy Region

Introduction: The blood alcohol concentration (BAC) is a crucial analysis for both patient health and legal implication. For the Italian law, the cut-off is set at 0 g/L or 0.5 g/L level, depending on the age of the patient. Aim of this paper was to present and comment the results obtained for ethanol concentration obtained by the Regional Coordination Center for Laboratory Medicine of the Lombardy Region (CRCMedLab) in the period 2020-2024. Methods: CRCMedLab manages External Quality Assessment (EQA) program for the analysis of ethanol in whole blood. Control material is provided by manufacturer and is constituted by certified spiked whole blood. CRCMedLab analyzed 51 samples submitted to the Laboratories enrolled in the scheme within the period 2020-2024 for a total of 1051 results. Results: The coefficient of variation (CV%) for the analyzed samples ranged from 3.64 to 18.78. For 26 samples with high target value (>0.8 g/L), the CV ranged from 3.74 to 14.99. Among 12 samples with negative target values (245 results), 1.22% provided false positive result. For 6 samples with target values between 0.1-0.5 g/L (126 results), CV ranged from 6.93 to 16.86. For 7 samples (144 results) with target values near the 0.5 g/L cut-off, the mean concentration was 0.49 g/L: 71 results (49.30%) exceeded the cut-off, while 73 results (50.70%) were below it. The CV for these samples ranged from 5.00% to 18.78%. Discussion: The laboratories participating in the EQA program demonstrate good performance, consistent with literature reports. EQA programs demonstrated a trend of improvement in CV over the years, although not conclusive. Due to the potential legal implication in the forensic field, the measurement uncertainty related to the data provided by laboratories deserves continuous investigation.