Propriedades psicométricas da versão brasileira do short form brief pain inventory (SF-BPI) em idosos com dor crônica e a relação com o lócus de controle da dor

Abstract

Pain is one of the causes of greater incapacity worldwide. Despite being such a prevalent condition on elders, its evaluation is still a challenging task and often times neglected, due to the misconception that the symptom is an inherent part of aging. In this context, the use of instruments for multidimensional pain assessment, such as the Short Form Brief Pain Inventory (SF-BPI), can allow a careful assessment of the symptom. Although the SF-BPI is an instrument widely used in the scientific and clinic international scenario, there were not found studies that have investigated the psicometric properties of its Brazilian version in community elderly, with chronic neuropathic, nociceptive and nociplastic pain. The beliefs and personal attitudes related to pain can also interfere with the individual behavior in the face of pain symptoms. The Locus of Control (LC) is a construct built to explain the perception or the belief of a person about who or what contains the control over certain aspects of life, including over the painful experience. The instrument Pain Locus of Control Scale - MHLC-Form C (PLOC-C) allows the classification of the LC in internal, chance, based on other people (family, friends) or health professionals, and the last three constitute subtypes of external locus of control (LCE). The evidences suggest that those with internal locus of control (LCI) of pain achieve the most positive results in terms of coping with the sympton. Therefore, the first objective of the study was to evaluate the psychometric properties of the Brazilian version of the SF-BPI in community-dwelling elderly people. The second objective was to investigate the association between the SF-BPI and the PLOC-C scale through a multiple linear regression analysis. To this end, two models were stipulated: pain intensity and pain interference. Both had the following independent variables: internal, chance, in other people and in health professionals LC. The dependent variables were the SF-BPI pain intensity score for the first model and the SF-BPI pain interference score for the second. It was then carried out an observational, methodological, cross-sectional study, which included a convenience sample of 114 elders with nociceptive, neuropathic and/or nociplastic chronic pain. Based on the results, it was possible to attest to the validity of the questionnaire construct by means of the confirmatory factor analysis, which ratified a 2-factor structure described in the literature. In addition, it was identified convergent validity between the similar ones of the SF-BPI and the Pain Intensity (PPI) scale, derived from the pain questionnaire “Mcgill”. Good global internal consistency of the SF-BPI was verified (Cronbach's α: 0.87), as well as its pain intensity and interference dimensions (Cronbach's α; 0.84 and 0.82, respectively). Excellent test-retest reliability was observed for mean pain intensity and interference scores (Intraclass Correlation Coefficient - ICC: 0.90 and 0.96, respectively). Inter-rater reliability was also excellent for both dimensions (ICC: 0.77). Regarding the LC and its classification according to the application of the PLOC-C, it was identified that 54% of the elderly had a predominant locus in other powerful others, 29.8% had an LCI and only 6.14% had a chance locus. Regarding the analysis of multiple linear regression, the results indicate that both the pain intensity model (F9-104= 2.982; p<0.05; R2=0.205) and pain interference model (F9-104= 5.905; p<0.01; R2= , 338) were statistically significant, which explained 20.5% and 33.8% of the variance of the respective SF-BPI scores. Among all the independent variables, only the LCI was able to predict intensity (β= -0.297; T= -3.292; P<0.01) and pain interference (β= -0.257; T= -3.131; P<0.05), with an inverse and significant association being observed between the LCI and the scores of each of the aforementioned dimensions of the SF-BPI. Thus, the study brought sufficient evidences that sustain the validity and reliability of the Brazilian version of the SF-BPI for community elderly dwellers with the painful phenotypes included in this research. It is a relevant data, considering the restrict number of questionnaires for the multidimensional pain evaluation already validated for this population on the country. In addition, it concludes that the associated use of the SF-BPI and the PLOC-C provides a more global overview of the painful phenomenon on elders, which may guide the adoption of therapeutic conducts that are in fact resolute.