Table 2.

Sensitivity and Specificity of Phosphatidylethanol (PEth) for Past-Month Drinking

Drinking State	PEth Concentration* (ng/mL)	Sensitivity (95% confidence interval)	Specificity (95% confidence interval)
Any drinking	≥8	79% (71–88)	90% (81–98)
Any drinking	≥ 20	73% (65–80)	96% (92–100)
≥ 4 drinks/day	≥ 20	97% (92–100)	66% (59–73)
≥ 4 drinks/day	≥80	91% (82–100)	77% (70–83)

^*The PEth concentrations represent the original and improved limits of PEth quantitation and the concentration that maximized sensitivity+specificity for averaging at least 4 drinks daily as described in the text.