Eindwerk psycho-oncologie 2016-2018: 'Alexithymia assessment in cancer care: A content validity study of the 20-Item Toronto Alexithymia Scale'

Objectives

Alexithymia - the inability to recognize and express emotions – has been observed among a wide range of psychiatric disorders, but also medical conditions such as cancer. Typically, the empirical research on alexithymia has measured the construct with the TAS-20, currently the most widely used self-report measure of alexithymia. However, questions have been raised on the (discriminant) content validity of this measure, that is whether it measures alexithymia in a relevant and comprehensive manner without contamination from related constructs. This study assessed the content validity and discriminant content validity of the TAS-20 items using the Discriminant Content Validity (DCV) methodology.

Methods

Via an online tool, participants (n = 81) were presented with the TAS-20 items and items of related constructs (i.e. anxiety, depression, and health anxiety). Items were rated against construct definitions (i.e. alexithymia, difficulty identifying feelings, difficulty describing feelings, externallyoriented thinking, limited imaginal capacity, anxiety, depression, and health anxiety) to determine whether they measured a particular construct (no/yes/yes, when reversed scored). Judges’ confidence in each assessment was also assessed (0-100%) and used to establish quantitative estimates of content validity for each item.

Results

Data of 74 participants were analyzed using linear mixed effects models. The results revealed that all items from the included anxiety, depression, and health anxiety measures assessed the intended construct well and scored significantly higher on the intended construct than on any other construct. This was not the case for the TAS-20 items, where only 10 out of the 20 items measured alexithymia. In particular, the majority of these items were equally well perceived as measures of both the difficulty identifying feelings and the difficulty describing feelings constructs. Two items were perceived as measures of health anxiety, of which one was also found to measure anxiety. The other TAS-20 items were not perceived by participants as measures of any of the overarching constructs. Only one item of the externally-oriented thinking scale was identified to measure the externally-oriented thinking construct.

Conclusions

Based upon current findings we can conclude that the TAS-20 may need some revision to adequately address all features of alexithymia. Furthermore, authors should be careful when using the TAS-20 with people suffering from anxiety complaints or debilitating diseases such as cancer with somatic complaints.