Evaluating acute pain intensity relief: challenges when using an 11-point numerical rating scale

Area of Science:

• Pain Management
• Clinical Measurement
• Emergency Medicine

Background:

• The percentage of pain intensity difference (PercentPID) is a common metric for assessing pain relief.
• However, PercentPID has limitations in accurately reflecting patient-reported pain relief.
• A novel metric, the slope of relative pain intensity difference (SlopePID), has been proposed to address these limitations.

Purpose of the Study:

• To validate the novel SlopePID metric against established measures of subjective pain relief.
• To compare the discriminative power and accuracy of SlopePID versus PercentPID.
• To determine optimal cutoffs for substantial pain relief using both metrics.

Main Methods:

• A prospective cohort study involving 361 emergency department patients with acute pain (NRS > 3).
• Pain intensity was assessed using an 11-point numerical rating scale (NRS) before and after analgesic administration (within 90 minutes).
• SlopePID was validated against a 5-category relief scale, a 2-category relief question, and a single-item question on medication need.

Main Results:

• Both PercentPID and SlopePID demonstrated similar discriminative power (AUCs 0.83 and 0.82, respectively).
• Substantial pain relief was defined as a 64% decrease for PercentPID and 49% per hour for SlopePID.
• PercentPID underestimated pain relief by 12.1% compared to SlopePID when using a 50% relief cutoff, particularly with odd baseline pain scores.

Conclusions:

• SlopePID is a more accurate and reliable metric for evaluating acute pain relief compared to PercentPID.
• The study recommends adopting SlopePID for pain assessment in clinical settings.
• SlopePID provides a more nuanced evaluation of pain relief, especially in the emergency department context.