Introduction Spinal cord stimulation is frequently used for the treatment of intractable chronic pain conditions. Trialing of the spinal cord stimulator device is recommended to assess the patient’s response to neurostimulation before permanent implantation. The trial response is often assessed by Numeric Rating Scale changes and patient-reported percentage pain improvement. Using number rating scale changes between prespinal and postspinal cord stimulation trial, a calculated percentage pain improvement can be obtained. The aim of this study was to assess the difference between calculated and patient-reported percentage improvement in pain scale during spinal cord stimulation trials.
Methods This study was a retrospective single center review of all spinal cord stimulation trials from January 1 2017 to July 1 2019. A total of 174 patients were included. The paired t-test was used to compare numeric pain scores obtained prestimulation versus poststimulation. The mean difference between methods (patient-reported minus calculated) was compared with zero using the 1-sample t-test. Lin’s concordance correlation coefficient was computed with a 95% CI, calculated using Fisher z-transformation; and a bootstrapping approach was used to compare the concordance correlation coefficient between groups. In all cases, two-tailed tests were used with p<0.05 considered statistically significant.
Results Based on prestimulation and poststimulation numeric rating scale scores, the mean±SD calculated percentage improvement in pain scale was 54±28. The mean±SD patient-reported percentage improvement in pain scale was 59±25. The overall 95% limits of agreement for the two methods are −30% to +41%. The overall concordance correlation coefficient was 0.76 (95% CI 0.69 to 0.81).
Conclusion Although the two methods are highly correlated, there is substantial lack of agreement between patient-reported and calculated percentage improvement in pain scale, suggesting that these measures should not be used interchangeably for spinal cord stimulator trial outcome assessment. This emphasizes the need for improved metrics to better measure patient response to neuromodulation therapies. Additionally, patient-reported percentage improvement in pain was found to be higher than calculated percentage improvement in pain, potentially highlighting the multidimensional experience of pain and the unpredictability of solely using Numeric Rating Scale scores to assess patient outcomes.
- spinal cord stimulation
- treatment outcome
- pain measurement
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Contributors JMH conceived the study. JMH, MB, NC and SC performed the data collection. JMH and DRS performed the statistical analysis. All authors contributed to manuscript preparation and agreed on the final version.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests JMH is a consultant for Abbott, Boston Scientific and Nevro. JMH is on a product advisory board for Boston Scientific. TD is a consultant for Abbott, Medtronic (Stimgenics), Vertos, Flowonix, Saluda Medical, SpineThera, Nalu, Cornerloc, Paintec, SPR Therapeutics and Boston Scientific (Vertiflex). TD is a member of the advisory board for Abbott, Flowonix, Nalu, SPR Therapeutics and Vertiflex. TD has equity options in Vertos, SpineThera, Saluda Medical, Nalu, Paintec and Cornerloc. TD has funded research from Abbott, Mainstay Medical, Saluda Medical, SPR Therapeutics and Vertiflex. TD has a patent pending for the DRG paddle lead with Abbott. MB has funded research from Nevro. SM has funded research from Abbott. NC, SC, DRS and WMH have no competing interests.
Patient consent for publication Not required.
Ethics approval The study was deemed exempt by the Mayo Foundation Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as online supplemental information. All relevant data were included in the manuscript.