Research report: Defining clinically meaningful pain reduction after spinal injections using an 11-point numerical rating scale and patient-reported relative reduction of pain

A new retrospective study from a spinal intervention center has now defined specific numerical thresholds that distinguish a substantial improvement from a minimal one, using both standard pain scores and patients' own impressions of relief. The research team analyzed data from 1,828 patients treated at their center who underwent spinal injections and completed a follow-up telephone interview two weeks later in 2017. From these scores, the researchers calculated three measures: the absolute reduction in pain score, the relative reduction as a percentage of the starting score, and a patient-reported relative reduction of pain, in which patients themselves estimated how much their pain had eased.

Patients also rated their overall recovery on a five-point global perceived effect scale, ranging from completely recovered to worsened. By comparing pain changes against these global ratings, the team established what a typical improvement looked like for each level of perceived benefit. Patients who said they were much improved reported an average absolute drop of 4.5 points on the pain scale, a relative reduction of about 65 percent, and a patient-reported relative reduction of roughly 68 percent.

Those who said they were only slightly improved reported much smaller changes: an average drop of 2.4 points, a relative reduction of about 37 percent, and a patient-reported reduction of about 36 percent. Receiver-operating-characteristic curve analysis then identified cutoff values that best predicted two clinically important outcomes. A substantial clinically important difference, corresponding to patients who were completely recovered or much improved, was predicted by an absolute pain score reduction of at least 3 points, a relative reduction of at least 50 percent, or a patient-reported relative reduction of at least 50 percent.

For a minimal clinically important difference, which included patients who were at least slightly improved, the thresholds were lower: an absolute reduction of at least 1 point, a relative reduction of at least 10 percent, or a patient-reported relative reduction of at least 20 percent. The findings give clinicians and researchers a practical framework for interpreting pain outcomes after spinal injections. The authors note that the thresholds were derived from a single center's patient population with two-week follow-up, so the values reflect short-term outcomes in that setting.

Subject of Research: Clinically meaningful pain improvement thresholds after spinal injections

Article Title: Defining clinically meaningful pain reduction after spinal injections using an 11-point numerical rating scale and patient-reported relative reduction of pain

Article References: Do, Y., Son, W., Kim, Y., Chee, C. G., Kang, Y., Lee, E., Kim, Y. J., & Lee, J. W. (2026). Defining clinically meaningful pain reduction after spinal injections using an 11-point numerical rating scale and patient-reported relative reduction of pain. PLOS One, 21(10), e0361475. https://doi.org/10.1371/journal.pone.0361475

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0361475

Keywords: spinal injections, pain measurement, numerical rating scale, clinically important difference, MCID, SCID, global perceived effect, patient-reported outcomes, retrospective study, pain management, Defining, clinically