Addiction Research and Theory August 2010; 18(4): 409–420 The use of the RCQ-D in patients with poly drug abuse VEERLE RAES 1 , GERDIEN A. DE WEERT-VAN OENE 2 , MARY M. VELASQUEZ 3,4 , JAN DE MAESENEER 5 ,& COR A. J. DE JONG 6 1 Department of Research and Quality Assurance, De Sleutel, Jozef Guislainstraat 43a, Ghent, Belgium, 2 UMC Utrecht, Julius Center, The Netherlands, 3 Center for Social Work Research, University of Texas at Austin/Health Behavior Research and Training Institute, Austin, USA, 4 School of Social Work, Austin, USA, 5 Family Medicine and Primary Health Care, Ghent University, Ghent, Belgium, and 6 Nijmegen Institute for Scientist Practitioners in Addiction, Radboud University Nijmegen, Nijmegen, The Netherlands (Received 6 March 2009; revised 26 August 2009; accepted 27 August 2009) Abstract Aim: The transtheoretical model is often used in substance abuse treatment planning. For polydrug abusing patients, operationalizing the stages of change is more difficult, as their readiness to change may differ depending on the substances. It was the aim of this study to investigate if the same structure of the Dutch Readiness to Change Questionnaire (RCQ-D) in a group of alcohol abusers could be found in an inpatient group of polydrug abusers for all substances. Design: For each substance, the structure of RCQ-D was tested using factor-analysis. Internal consistency was evaluated with Cronbach’s alpha. Mean scores were calculated to evaluate conformity with stage assignment. Around 305 polydrug abusers completed 1248 RCQ-D during their first week of stay. Findings: The RCQ-D had a different, but interpretable structure from the expected one. A two-factor structure was found for alcohol, nicotine and opiates, a three-factor structure for benzodiazepines, cannabis, methadone and cocaine. The underlying construct, based on the transtheoretical model, seemed to fit for alcohol and nicotine. There were some problems of stage allocation for benzodiazepines, cannabis and methadone. But, people in action could be distinguished from those not in action. More serious problems of allocation were found for opiates and cocaine. Conclusions: RCQ-D can be used to measure polydrug abusers’ thinking and use-behaviour separately by substance. The validity of RCQ-D to assign stages in case of opiates and cocaine is unclear. Keywords: Readiness for change, multiple substance abuse, RCQ-D, psychometric characteristics, inpatient motivation centre Correspondence: Veerle Raes, Department of Research and Quality Assurance, De Sleutel, Jozef Guislainstraat 43a, Ghent, 9000 Belgium. Tel.: þ32 9 2108725. Fax: þ32 9 2728611. E-mail: veerle.raes@fracarita.org ISSN 1606-6359 print/ISSN 1476-7392 online ß 2010 Informa UK Ltd. DOI: 10.3109/16066350903291066