Stability of Phosphatidylethanol 16:0/18:1 in Freshly Drawn, Authentic Samples from Healthy Volunteers

Due to its specificity, phosphatidylethanol (PEth) 16:0/18:1 has gained increased popularity as a marker for high alcohol consumption in recent years. As conflicting results regarding the stability of PEth 16:0/18:1 in whole blood have been published, there are still uncertainties related to optimum handling, transport and storage of blood samples for the analysis of PEth 16:0/18:1. A stability study where whole blood samples were drawn from healthy volunteers, who had ingested alcohol, is presented. The samples were collected in tubes with ethylenediamine tetraacetic acid (EDTA) and heparin as additives and stored under standardized conditions within 1 h of blood sampling. Storage times were 28 days in ambient temperature and at 4-8°C, and 90 days at -20°C and -80°C. All samples were analyzed regularly during the storage periods. PEth 16:0/18:1 concentrations were stable (defined as < 15% decrease compared with baseline values) at all temperatures up to 28 days, independent of additive. After 90 days of storage at -20°C, the mean concentrations had decreased by 18.8% in EDTA tubes and by 13.8% in heparin tubes. At -80°C, the concentrations were stable throughout the 90-day period. The present study shows that in samples containing PEth formed in vivo, PEth 16:0/18:1 is stable for 28 days irrespective of storage temperature. During long-term storage, samples should be stored at -80°C.