Our primary explanatory variable was alcohol exposure, which was characterized using two different alcohol exposure measures, separately and combined: (i) self-reported AUDIT-C; and (ii) PEth. AUDIT-C data were collected as part of a confidential self-administered survey conducted at VACS enrolment and during annual follow-ups. PEth assays were performed on dried blood spot samples by United States Drug Testing Laboratories (USDTL), in Des Plaines, IL, using a previously reported method.34 A positive PEth (measuring phosphatidylethanol species 16:0/18:1) indicates alcohol exposure for up to approximately 21 days prior to sample collection.22,35
