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Response Rates: Study interviews were conducted with about 42 percent of the eligible powder cocaine users, 70 percent of the eligible crack users, and 52 percent of the eligible heroin users, although there was substantial variation by site and gender. In addition, two separate interviews were completed with about 63 percent of the eligible heroin-and-powder cocaine users and 57 percent of the eligible heroin-and-crack users.应答率：本研究对符合入选标准的粉末可卡因（powder cocaine）使用者完成了约42%的访谈，对符合入选标准的快克可卡因（crack）使用者完成了约70%的访谈，对符合入选标准的海洛因（heroin）使用者完成了约52%的访谈，但不同研究地点与性别间存在显著差异。此外，约63%符合入选标准的海洛因-粉末可卡因联用使用者、57%符合入选标准的海洛因-快克可卡因联用使用者完成了两次独立访谈。