In the present study, a cross-cultural adaptation of the CSI, from English to the Spanish, was completed, resulting in a CSI-Sp version of this Inventory. Construct validity and internal consistency of the CSI-Sp were determined independently, and were both found to be strong. The single factor structure from this psychometric properties indicated that a single summated score could be used (Doward and McKenna 2004). The one-factor solution that emerged in the factor analysis accounted for a significant proportion of variance, and showed evidence supporting the presence of construct validity. The findings of the current study, however, is contrast with the English (Mayer et al. 2012), Dutch (Kregel et al. 2015), and French (Pitance et al. 2016) versions. The first two versions revealed a 4-factor model, and the French version produced 5-factors. However these studies did not satisfy the three point requirements for extraction, as recommended by Costello and Osborne 2005 and in the other hand, our study shown a low variance explained (Costello and Osborne 2005). Both English and Dutch versions demonstrated 3 (Garratt 2009; Heinricher et al. 2009; Costello and Osborne 2005; Terwee et al. 2007) or 5 (Garratt 2009; Heinricher et al. 2009; Kregel et al. 2015; Stratford 2004) items with an insufficient load on any factor. A one-factor solution is critical if a PRO is used with a single summated score, and it subsequently reflects the construct for which it is primary employed—that of representation of the only CS condition.
High test–retest reliability, was found (ICC = 0.91), which was in-line with the test–retest results of the English (0.82) (Mayer et al. 2012), Dutch (0.88) (Kregel et al. 2015) and French versions (0.91–0.94) (Pitance et al. 2016). Consequently, the current study shows that the CSI-Sp should prove to be a reliable instrument. Internal consistency analysis showed a level of 0.872, below the accepted 0.95 thresholds for item redundancy (Terwee et al. 2007). Similarities were found in the internal consistency of all 25 items of the CSI in the original study of the English version (Cronbach’s α = 0.879) (Mayer et al. 2012) and the Dutch version (Kregel et al. 2015) (Cronbach’s α = 0.91).
This present translation proportionated accessibility to the CSI-Sp for the second largest geographically-used language (United Nations 2016) A cross-cultural adaptation of a scale has been previously done to be applied in the Spanish context (Muñiz et al. 2013). It is critical to employ valid and reliable research measures which are culturally and linguistically appropriated.
The strengths of the present study included its prospective nature and adequate number of subjects; the inclusion of consecutive patients; and the limited selection bias (Kass and Tinsley 1979). Obtaining results supporting the psychometric properties of the previous research on the original English version indicates that may it be possible to compare Spanish and English population and that cross-cultural adaptions would be appropriate to other diverse linguistic groups.
One limitation of the present study is the lack of longitudinal data regarding other psychometric properties and not including Hispanic/Latino/South American participants, which would have potentially provided confirming or conflicting linguistic information. Hence, it would be appropriate to include them in futures studies. Other limitation was the sample size to run Confirmatory Factor Analysis focussing to identify the best factor structure, in this way we are started a pool of data (n > 2000) across the different countries/languages (US, Spain, Belgium, France, Serbia, Italy and Brazil).