Cross-sectional assessments of participants' characteristics and loss to follow-up in the first Opioid Substitution Therapy Pilot Program in Kabul, Afghanistan. - Ruiseñor-Escudero H; Vu A; Wirtz AL; Familiar-Lopez I; Berry M; Mfochive I; Engineer C; Farhad A; Tschakarjan S; Wisse E; Paikan FM; Burnham G (Harm reduction journal, 2015)