Psychometric Properties of the Pictorial Pain Interference Questionnaire for Assessing Functional Interference in Chronic Low Back Pain.

Abstract

To analyze the psychometric properties of the Pictorial Pain Interference Questionnaire (PPIQ) for evaluating functional interference in the population with chronic low back pain (CLBP). Cross-sectional study. Rehabilitation Unit in a hospital. Ninety-nine patients with CLBP. Not applicable. Functional interference was assessed using PPIQ. The following data were also collected: sociodemographic data; pain intensity (Numeric Pain Rating Scale [NPRS]); physical functioning (30-s arm curl, 30-s chair stand [30CST], and timed Up and Go [TUG] tests), fitness (International Physical Activity Questionnaire); quality of life (Short-Form 12 Health Survey version 1 [SF-12v1]); sleep quality (Spanish-validated 12-item Medical Outcomes Study Sleep scale [12-MOS Sleep]); anxiety and depression (Hospital Anxiety and Depression Scale [HADS]); and social support (Duke-UNK Functional Social Support Questionnaire). Internal consistency was analyzed using Cronbach's alpha, structural validity using exploratory factor analysis (EFA), and discriminant and convergent validity using bivariate analysis. Ninety-nine patients with CLBP were included (age [mean ± SD]: 54.37±12.44 y); women, 67.7%). The EFA extracted 2 factors: "physical function and "social and sleep," which explained 57.75% of the variance. Excellent internal consistency was observed for the overall PPIQ score (Cronbach's α=0.866). Convergent validity was observed between the PPIQ and other functional measures (ρ: 0.52 and -0.47 for the TUG and 30CST, respectively; P<.001) and with the following variables: physical and mental component summaries of the SF-12v1 (ρ: -0. 55 and -0.52, respectively (P<.001); anxiety and depression of the HADS (ρ: 0.47 and 0.59, respectively (P<.001); NPRS (ρ: 0.45; P<.001); and index 9 of the 12-MOS Sleep scale (r: 0.49; P<.001). The PPIQ is a valid instrument with good psychometric properties for measuring functional interference in people with CLBP. This questionnaire appears to be a feasible alternative when language or communication barriers exist in CLBP population.