Sensitivity and specificity of EtG in hair as a marker of chronic excessive drinking: pooled analysis of raw data and meta-analysis of diagnostic accuracy studies.

Background: To assess the debated diagnostic performance of ethyl glucuronide in the 3-cm proximal scalp hair fraction (HEtG) as a marker of chronic excessive drinking.

Methods: In July 2012/May 2013, after a systematic search through the MEDLINE, OVID/EMBASE, WEB OF SCIENCE, and SCOPUS databases, 8 studies were included in the pooled analysis that report raw single data on HEtG concentration and self-reported daily alcohol intake (SDAI). A receiver operating characteristic curve analysis and a Spearman rank-order correlation test were used. A meta-analysis was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Cochrane recommendations, comprising quality and bias assessments.

Results: The pooled analysis showed that 30 pg/mg could be a useful cutoff value for HEtG to detect an SDAI >60 g/d and demonstrated a parabolic direct correlation between HEtG and SDAI data [rho 0.79; 95% confidence interval (CI), 0.69-0.87; P < 0.001]. The meta-analysis found an overall HEtG sensitivity of 0.96 (95% CI, 0.72-1.00) and a specificity of 0.99 (95% CI, 0.92-1.00); a nomogram to predict the posttest probability of exhibiting the targeted condition in the general population was built. Significant variability among the included studies was detected, which was mainly explained by true heterogeneity in the presence of publication bias.

Conclusions: With the available data, we conclude that HEtG is a promising marker for identifying chronic excessive drinking. Nonetheless, larger and well-designed population studies are required to draw any definitive conclusions on the significance and appropriateness of its application in the forensic setting.