Relative and absolute reliability of a vertical numerical pain rating scale supplemented with a faces pain scale after stroke

Background. Pain is a serious adverse complication after stroke. The combination of a vertical numerical pain rating scale (NPRS) and a faces pain scale (FPS) has been advocated to measure pain after stroke. Objective. This study was conducted to investigate whether an NPRS supplemented with an FPS (NPRS-FPS) would show good test-retest reliability in people with stroke. The relative and absolute reliability of the NPRS-FPS were examined. Design. A test-retest design was used for this study. Methods. Fifty people (>3 months after stroke) participating in an outpatient occupational therapy program were recruited through medical centers to rate current pain intensity twice, at a 1-week interval, with the NPRS-FPS (on a scale from 0 to 10). The relative reliability of the NPRS-FPS was analyzed with the intraclass correlation coefficient for determining the degree of consistency and agreement between 2 measures. The standard error of measurement, the smallest real difference, and Bland-Altman limits of agreement were the absolute reliability indexes used to quantify measurement errors and determine systematic biases of repeated measurements. Results. The relative reliability of the NPRS-FPS was substantial (intraclass correlation coefficient=.82). The standard error of measurement and the smallest real difference at the 90% confidence interval of the NPRS-FPS were 0.81 and 1.87, respectively. The Bland-Altman analyses revealed no significant systematic bias between repeated measurements for the NPRS-FPS. The range of the limits of agreement for the NPRS-FPS was narrow (-2.50 to 1.90), indicating a high level of stability and little variation over time. Limitations. The pain intensity of the participants ranged from no pain to a moderate level of pain. Conclusions. These findings suggest that the NPRS-FPS is a reliable measure of pain in people with stroke, with good relative and absolute reliability.