Validation of Self-Reported Pain Reduction After Diagnostic Blockade

Objective. The criterion commonly used to determine whether radiofrequency neurotomy may be recommended is based on patient-reported, short-term pain relief following facet block injections. This study evaluated the concordance between two commonly used outcomes for pain relief: the pain numerical rating scale (NRS) and the global perceived improvement (GPI) scale. Design. This is a retrospective cohort study. Methods. Data were obtained from a consecutive cohort of patients through a review of the electronic medical records, with the following inclusion criteria: medial branch facet blocks at either cervical or lumbar spinal regions. Outcome Measures. Pain NRS (baseline, postprocedure, and hourly up to 6 hours) and GPI scale are expressed as percent improvement at 6 hours, relative to baseline. Results. The percent improvement in pain NRS corresponded to 49%, 43%, 34%, 21%, and 36% for baseline vs immediately post-block, 1 hour, 3 hours, 6 hours and average of all postscores, respectively. Average GPI reported at 6 hours was 44%, and differed significantly only to the baseline vs 6 hours percent improvement on the NRS (P<0.01). Multiple regression analysis indicated that there were no demographic or baseline factors that accounted for the discrepancy between GPI vs NRS. Conclusions. Asking patients about their pain relief in retrospect can be misleading. It is possible that patients' report on the GPI is weighed by their total experience of pain reduction and retrospective recall. Therefore, when choosing to address percent improvement on NRS measures, it is important to take into account multiple instances of NRS measures following treatment.