Original Article Reliability and validity of the Persian adaptation of the Core Outcome Measure Index in patients with chronic low back pain Noureddin Nakhostin Ansari a, * , Soofia Naghdi a , Zahra Eskandari a , Nasser Salsabili a , Ramin Kordi b , Scott Hasson c a Department of Physiotherapy, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran b Sports Medicine Research Centre, Tehran University of Medical Sciences, Tehran, Iran c Department of Physical Therapy, Georgia Regents University, Augusta, GA, USA article info Article history: Received 25 March 2016 Received in revised form 29 June 2016 Accepted 26 July 2016 Available online 18 August 2016 abstract Background: The purpose of the study was to determine whether the Persian Core Outcome Measures Index (PCOMI) is reliable and valid in patients with chronic low back pain (CLBP). Methods: The Persian COMI was developed using forward-backward translational method. Subjects were100 patients with CLBP. Patients completed the PCOMI, Persian functional rating index, and visual analog scale. Fifty patients completed the PCOMI for the second time after 7days to evaluate test-retest reliability. Fifty healthy subjects participated to assess discriminant validity. Results: There was no ceiling or floor effect. Cronbach's alpha was 0.85. The construct validity coefficient was 0.72. The ICC agreement for test-retest reliability was 0.86. Pearson correlation for criterion validity was 0.70. The PCOMI discriminated between patients and healthy subjects. The standard error of measure- ment and the smallest detectable change was 0.75 and 2.1, respectively. Factor analysis extracted 1 component. Conclusions: The results support the reliability and validity of the PCOMI for assessing patients with CLBP. © 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved. 1. Introduction Chronic low back pain (CLBP) is a common, disabling condition which approximately affects 70e85% of the adult population and can negatively impact the quality of life [1,2]. To quantify the effectiveness of treatment, reliable and valid tools must be used. Currently, self-report questionnaires have been suggested for evaluating the level of function and disability in patients with LBP. Self-reported functional questionnaires are inexpensive and simple to use instruments which provide meaningful as well as quantita- tive data [3]. Several functional status questionnaires have been developed to evaluate the functional outcome of therapeutic intervention in LBP [4,5]. To promote more standardization of outcome measurements in various types of studies, an international group of back pain researchers recommended the Core Outcome Measures Index (COMI) as a short self-administered multidimensional question- naire to assess patients with LBP [6]. The COMI has demonstrated sound psychometric properties of validity, reliability, and respon- siveness [6e8] which is adapted and validated for use in various countries [8e15] (Table 1). The present study aimed to translate and cross-culturally adapt the COMI into Persian language and to test the psychometric properties of the Persian COMI in patients with CLBP. 2. Materials and methods The procedure recommended for translation and cross-cultural adaptation of health questionnaires was followed to produce the Persian version of the COMI [16] as used Previously [17e19]. Briefly, two professional translators, one of them not familiar with the COMI, independently translated the COMI to Persian language. The synthesized Persian COMI produced by the expert committee was back translated to English by another two independent translators. Finally, the committee of experts reviewed all documents including * Corresponding author. Department of Physiotherapy, School of Rehabilitation, Tehran University of Medical Sciences, Enghelab Ave, Pitch-e-shemiran, 11489 Tehran, Iran. Fax: þ98 21 77727009. E-mail address: nakhostin@sina.tums.ac.ir (N. Nakhostin Ansari). Contents lists available at ScienceDirect Journal of Orthopaedic Science journal homepage: http://www.elsevier.com/locate/jos http://dx.doi.org/10.1016/j.jos.2016.07.022 0949-2658/© 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved. Journal of Orthopaedic Science 21 (2016) 723e726