Cross-cultural adaptation and validation of Pamela Reed’s Self-Transcendence Scale for the Spanish context*

ABSTRACT Objectives: the current study aimed to adapt the Self-Transcendence Scale (STS) to the Spanish context and analyse its psychometric properties. Method: the STS was administered to a general Spanish population of adults (i.e., older than 20 years; n = 116) through an online platform. The Psychological Well-Being (PWB) and the Functional Assessment of Chronic Illness Therapy - Spiritual Well-being - modified version for healthy people (FACIT-Sp-Non-Illness) scales were also applied in two moments separated by an interval of 15 days. Results: the results of the validation included the following statistics: αt = 0.772 (test) and αrt = 0.833 (retest); ICC = 0.278 (p = 0.097, intraclass) and 0.932 (p < 0.001, interclass); a Bland-Altman confirmation of the test/re-test (TRT) concordance; global content validity coefficient (S-CVI) = 0.92; r 1 = 0.636 (PWB) and r 2 = 0.687 (FACIT-Non-Illness; both p < 0.001); and three factors explained 42.3% of the variance. The STS showed positive apparent validity and feasibility. Conclusions: the Spanish version of the STS is valid for use in the general population, with updates relative to the Colombian version that include more natural wordings, syntactic corrections, inclusive language, a better definition of the concepts, and an alternative factor model.

The STS is currently a consolidated scale that has been translated into different languages as Korean, Swedish, Persian or Norwegian (3)(4)(5)(6) ; however, this scale has not been adapted to the Spanish context. One reference exists regarding a version for adolescents adapted to the Colombian context, although the articles that have cited this paper are unpublished manuscripts (7)(8) . A cross-cultural adaptation and validation in the Colombian context was found (9) , and this reference is the only one in the Spanish language, showing an internal validity of α = 0.85.
Self-transcendence theory favours a humanistic approach to nursing that starts with prioritising a set of technical skills and moves to others that promote an internal process that exists within and between complex human systems. Its use in Spain might spur the beginning of new investigations that complement this view. For all these reasons, a cross-cultural adaptation of the scale and its validation for future studies related to this subject was considered pertinent.
The general objective of this study was to adapt understandable by a 12-year-old student (10) . The chatstep.com platform was used to discuss differences and reach agreement. Throughout the process, the methodological recommendations regarding the cross-cultural adaptation of evaluation scales were followed (10)(11)(12) .
The content validity of the STS was examined by a group of 20 experts. The inclusion criteria for participation on this panel were university graduates in nursing or psychology, experts in research, and native Spanish speakers. The experts received the questionnaire via e-mail and (a) assessed the conceptual 1 represents "irrelevant" and 4 represents "highly relevant"); and (c) provided suggestions and comments.
A content validity analysis was performed via the content validity index (I-CVI, where adequate validity ≥ 0.8 for each item) and the global content validity coefficient (S-CVI, where adequate validity ≥ 0.8 for the complete questionnaire) (13)(14) .
Finally, the feasibility and psychometric properties of the questionnaire were studied. The scale was administered to a sample of volunteers who were 20 years old or above. This criterion was verified during the administration of the scale, which was conducted through the application onlineencuesta.com, a previous dissemination via social networks and national nursing schools, and via promotional posters at the university, and health and social centres of Alcalá de Henares in Madrid, Spain. Two criteria were followed regarding the sample size: a minimum of 50 cases or 5-10 individuals per item (15) , which indicated a minimum of 75 cases Internal consistency was studied using Cronbach's alpha The statistical analyses were executed with the statistical packages "R Commander", "irr", "psych", "RCmdrPlugin.Survival", and "RCmdrPlugin. was modified, and the translation was adjusted following the suggestions provided (e.g., "physical condition" replaced "physical capabilities" and "as I become a senior" replaced "as I grow older", among others). Thus, the definitive version with which the content validity analysis was performed was obtained, and the results are displayed in Table 1.  Table 2.  The individual fit of the items to each factor (R 2 ) revealed a better global fit for the three-factor model, followed by the two-, four-, and one-factor models in that order.
At least one factor was negatively correlated in all the models, with progressively higher values as the number of factors extracted decreased (-0.26 in the four-factor model to -0.46 in the two-factor model). The CFA added goodness-of-fit indices to all of the models (Table 4).   The experts and participants also cited the need to clarify "spiritual beliefs" (item 12). We considered that discriminating between spirituality and religiosity is necessary in light of the religious situation in Spain.
According to the last barometer of the Centre for  In addition, few volunteers were available to select as translators and experts. Although the methodology suggested that bilingual and bicultural translators be used for both phases (12) , this was only possible for the reverse translation; nevertheless, this criterion is only recommended and not considered essential.
The Colombian reference version (9) presented similar results, with differences in the factorial structure (a single factor explained 36.18% of the variance).

Conclusions
The results of this study justify the validity and applicability of this scale in Spain. Although this line of research should be continued with appropriate adjustments, we conclude that a starting point already exists, which implies that the research objective (to elaborate the Spanish version of the STS) was fulfilled.