• John D Childs, Sara R Piva, and Julie M Fritz.
• Department of Physical Therapy, Wilford Hall Medical Center, San Antonio, TX, USA. childsjd@bigfoot.com
• Spine. 2005 Jun 1;30(11):1331-4.

Study DesignCohort study of patients with low back pain (LBP) receiving physical therapy.ObjectiveTo examine the responsiveness characteristics of the numerical pain rating scale (NPRS) in patients with LBP using a variety of methods.Summary Of Background DataAlthough several studies have assessed the reliability and validity of the NPRS, few studies have characterized its responsiveness in patients with LBP.MethodsDetermination of change on the NPRS during 1 and 4 weeks was examined by calculating mean change, standardized effect size, Guyatt Responsiveness Index, area under a receiver operating characteristic curve, minimum clinically important difference, and minimum detectable change. Change in the NPRS from baseline to the 1 and 4-week follow-up was compared to the average of the patient and therapist's perceived improvement using the 15-point Global Rating of Change scale.ResultsThe majority of patients had clinically meaningful improvement after both 1 and 4 weeks of rehabilitation. The standard error of measure was equal to 1.02, corresponding to a minimum detectable change of 2 points. The area under the curve at the 1 and 4-week follow-up was 0.72 (0.62, 0.81) and 0.92 (0.86, 0.97), respectively. The minimum clinically important difference at the 1 and 4-week follow-up corresponded to a change of 2.2 and 1.5 points, respectively.ConclusionsClinicians can be confident that a 2-point change on the NPRS represents clinically meaningful change that exceeds the bounds of measurement error.

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