Evaluation of the responsiveness of outcome measures after spine injection: A retrospective study

Discrepancies in patients' responses to various outcome measures challenge clinicians' evaluation of treatment outcomes. Therefore, we aimed to 1) evaluate the concordance of outcome measures after spine injection, 2) determine the patient variables that lead to discordant responses, and 3) suggest practical outcome measure for spine injections with good responsiveness. From October 2014 to November 2014, 164 patients with neck or low back pain who visited our outpatient clinics and had spine injections on the previous visit were enrolled. We asked patients to report changes in their symptom in the form of outcome measures: numeric rating scale, Oswestry disability index, neck disability index, residual symptom percentage and global perceived effect. The responses were categorized into three groups according to the degree of change; not improved, minimally improved, and significantly improved. The concordances of these categorized answers were evaluated. When "significantly improved" was considered as true improvement, 46 (28%) of the 164 patients had discordant responses to the four measures. There was no significant patients' variable that affects discordance in the outcome measures. Good agreement was shown between the global perceived effect and residual symptom percentage, while the Oswestry disability index had poor agreement with the other measurements. The calculated numeric rating scale and residual symptom percentage also had low levels of agreement. However, patients with severe pre-treatment pain tended to have better agreement. In conclusion, this result suggest that the residual symptom percentage may be a more practical for clinicians and better represent patients' improvements after spine injection.