Introduction Knee OA is the leading cause of pain and disability and half of people with knee OA experience significant pain that hinders daily activities. In the assessment of knee OA pain, the current focus is on pain intensity and associated disability, suggesting that the assessment of one dimension will reflect the other dimensions of chronic knee OA pain adequately. However, current studies dispute this assumption by showing fair correlation between scores on unidimensional disease-specific pain questionnaires and multidimensional ones. Appropriate pain measurement is critical to guide clinical decision-making. However, itï¿½s been reported that no attempt has been made to ask patients with pain about whether current outcome measures are meaningful or whether the instructions, anchors or items included in the scales are capturing their pain experience adequately. The objective of this study is to determine if people with knee osteoarthritis (OA) prefer one of three self-report pain measures addressing different pain dimensions to represent their pain experience. Secondary objectives were to examine the correlation among measures and burden of completing these measures. Method Participants attending an orthopaedic outpatient clinic aged 40 y or older having idiopathic knee OA pain, minimal pain in other body parts, fluent in English, and cognitively competent were recruited for our cross sectional study. All consenting participants completed a demographic form and three pain measures were administered in a pre-determined order. The pain measures included 1) a generic, 11-point, single-item measure (Verbal Numeric Rating Scale, VNRS, maximum score = 10) asking about average pain intensity in the study knee in the past 24 hours; 2) a disease-specific, multi-item questionnaire (Intermittent and Constant Osteoarthritis Pain Questionnaire, ICOAP, maximum score = 44) asking about intensity and consistency of pain in the study knee over the past week; and 3) a generic, multi-item questionnaire (Short-Form McGill Pain Questionnaire-2, SF-MPQ-2, maximum score = 10) asking about somatic and affective dimensions of pain in the study knee over the past week. Higher scores indicate worse pain for all measures. After completing each measure, participants were asked how the measures fit their pain experience (FIT) by rating how well the pain measure described their experience of pain by placing a horizontal mark on a 10 cm FIT visual analogue scale where 0 = ï¿½Does not describe my pain at allï¿½ and 100 = ï¿½Describes my pain completelyï¿½. FIT scores for the three measures were compared using Freidmanï¿½s nonparametric repeated measures analysis of variance test. Associations between raw scores on the three pain measures were tested using Spearman rho correlation (rs). Findings 96 participants (57 females) had a mean (SD) age of 63.8(9.4) yr. The median of FIT score for the VNRS, ICOAP and SF-MPQ-2 was 7.5, 7.4, and 7.8cm, respectively, and did not differ (Ï?2 (2, N = 96) = 1.288, P = 0.5). The included participants had moderate knee OA pain intensity (median (IQR) score =6(5), 23(14.5), 2.4(3) for VNRS, ICOAP and SF-MPQ-2). Scores on the three measures were similarly associated (VNRS and ICOAP: rs=0.73(0.62, 0.81); VNRS and SF-MPQ-2: rs=0.69(0.56, 0.78); ICOAP and SF-MPQ-2: rs=0.70(0.58, 0.79). Conclusion: All three pain measures describe knee OA pain experience to a similar degree and scores were only moderately correlated. Differences in the pain attributes assessed may explain the finding that no one measure represented the experience of knee OA pain better than the other measures in our study sample.
Ahmed Negm, Joy c. MacDermid, Paul W. Stratford, Mohit Bhandari, Mitch Winemaker, Justin de Beer, Norma MacIntyre
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