The Effect of Prolonged Storage Time on the Stability of Fatty Acid Ethyl Esters in Hair Samples

Abstract

The advantages of analysis of drugs in hair samples are recognised for the long window of detection, alongside easy sampling and long stability after sample collection. Alcohol markers, ethyl glucuronide (EtG) and total fatty acid ethyl esters (FAEEs) in hair are widely used for monitoring alcohol consumption for clinical and forensic purposes. Although stability of drugs and EtG in hair samples are documented to a certain extent, stability of FAEEs in hair samples after collection has not been reported. This study covered hair samples that had been tested for FAEEs on the day of arrival at the laboratory and retested between 4 days to 80 months later. The statistical analysis of the data set reveals significant lower FAEEs levels including ethyl palmitate ester levels (EtPa) when samples were re-tested for the second time after 6 days of storage under ideal conditions. Specifically, the results suggest that when measuring total FAEEs or solely EtPa in hair samples, the elapsed time between sample collection and analysis of the sample needs to be considered when interpreting the results. The recommendation is that whenever hair samples need to be tested for total FAEEs or EtPa, the analytical procedure needs to be performed within one week after collection in order to obtain meaningful results. The study results substantiate the case for the use of hair samples solely for the analysis of EtG, in conjunction with other measurements alcohol consumption such as full blood count (FBC), carbohydrate-deficient transferrin test (CDT), liver function test (LFT) or phosphatidylethanol (PEth) alongside clinical assessment for a more effective evaluation of alcohol consumption.

Testing venous carbohydrate‐deficient transferrin or capillary phosphatidylethanol with concurrent ethyl glucuronide and ethyl palmitate hair tests to assess historical and recent alcohol use

“…Even though EtPa is normally used to support EtG results when chemical cosmetic hair treatment may have depleted EtG levels, it is likely to be sufficient to use PEth test in combination with hair EtG alone. This is particularly pertinent because EtPa may falsely indicate abstinence if samples are stored for prolonged periods before analysis or may show positive results with certain hair products 3,11 . It was not possible to exclude the possibility of false‐positives findings for EtPa related to use of alcoholic hair care products, because the information provided at the point of collection and annotated in the sample pack chain of custody did not contain the necessary level of detail of the ingredients used.…”

“…Tests for EtG and EtPa in hair samples and PEth (16:0/18:1 homologue) in capillary blood covered by this study were performed utilising Cansford Laboratories in‐house LC–MS/MS methods that were validated and accredited to ISO/IEC 17025 standards for specificity, sensitivity, linearity, accuracy, precision and recovery. Hair EtG and EtPa tests were performed according to previously described methods, 10,11 and the method for the analysis of PEth in DBS was performed by using the LC–MS/MS method described by Jones et al 12 with minor modifications. The stability of PEth in DBS stored at room temperature was demonstrated by several researchers as being up to 6 months 12,13 .…”

Monitoring the use of alcohol—A critical overview of the state‐of‐the‐art biomarkers

“…As is the case for EtG, the concentration of ethyl palmitate (and other FAEEs) in hair can be influenced by chemical and/or thermal hair treatments (e.g., bleaching, dyeing, or perming) (Nanau & Neuman, 2015). Moreover, a recent study recommended that whenever hair samples need to be tested for FAEEs this should be done within 1 week after collection due to poor stability (Tsanaclis et al, 2020).…”