RESUMEN
OBJECTIVE: 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). DESIGN: Cross-sectional study. SETTING: Rehabilitation Unit in a hospital. PARTICIPANTS: Ninety-nine patients with CLBP. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: 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. RESULTS: 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). CONCLUSIONS: 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.
