[What does the pain self-efficacy questionnaire (German adaption, FESS) assess? : Studies on construct validity]

The German version of the pain self-efficacy questionnaire (FESS) is considered as an operationalization of this construct. Overlaps with pain acceptance, psychological flexibility, and accommodative coping raise questions regarding construct validity. This was investigated by examining the associations of the FESS with these constructs and with general self-efficacy expectations.

The FESS was administered to 357 patients with chronic pain participating in a day clinic interdisciplinary multimodal pain therapy (IMST). Exploratory factor analyses and correlation analyses were used to examine associations with the similar construct of general self-efficacy expectations (general self-efficacy scale, SWE) and to assess distinctness from related constructs of pain acceptance (chronic pain acceptance questionnaire - German version, CPAQ-D) and pain-specific psychological flexibility (German pain solutions questionnaire, PaSol).

A joint factor analysis of FESS and SWE items did not yield a homogeneous item set. In subsequent factor analyses, FESS items, CPAQ-D items, and PaSol subscales related to accommodative coping formed a shared item pool. Correlation analyses indicated less conceptual overlap between SWE and FESS (ρ = 0.403) - within the construct of self-efficacy - compared to stronger overlaps between FESS and the CPAQ-D subscale activity engagement (ρ = 0.803), the CPAQ-D overall score (ρ = 0.766), and the PaSol subscale meaning of life despite pain (ρ = 0.689).

The results indicate that the FESS does not fully capture the width of pain-specific self-efficacy. Conceptual overlaps are evident with instruments assessing pain acceptance, pain-specific psychological flexibility, and accommodative coping. These findings cast doubt on the content validity of the FESS. The FESS should be critically examined for assessing pain-specific self-efficacy expectations, and the findings obtained should be interpreted carefully. The necessary development of content-valid instruments requires a consensus-based definition of terms and the consistent involvement of patients.