title: Evaluating acute pain intensity relief: challenges when using an 11-point numerical rating scale.
abstract: Percentage of pain intensity difference (PercentPID) is a recognized way of evaluating pain relief with an 11-point numerical rating scale (NRS) but is not without flaws. A new metric, the slope of relative pain intensity difference (SlopePID), which consists in dividing PercentPID by the time between 2 pain measurements, is proposed. This study aims to validate SlopePID with 3 measures of subjective pain relief: a 5-category relief scale (not, a little, moderate, very, complete), a 2-category relief question ("I'm relieved," "I'm not relieved"), and a single-item question, "Wanting other medication to treat pain?" (Yes/No). This prospective cohort study included 361 patients in the emergency department who had an initial acute pain NRS > 3 and a pain intensity assessment within 90 minutes after analgesic administration. Mean age was 50.2 years (SD = 19.3) and 59% were women. Area under the curves of receiver operating characteristic curves analyses revealed similar discriminative power for PercentPID (0.83; 95% confidence interval [CI], 0.79-0.88) and SlopePID (0.82; 95% CI, 0.77-0.86). Considering the "very" category from the 5-category relief scale as a substantial relief, the average cutoff for substantial relief was a decrease of 64% (95% CI, 59-69) for PercentPID and of 49% per hour (95% CI, 44-54) for SlopePID. However, when a cutoff criterion of 50% was used as a measure of pain relief for an individual patient, PercentPID underestimated pain-relieved patients by 12.1% (P < 0.05) compared with the SlopePID measurement, when pain intensity at baseline was an odd number compared with an even number (32.9% vs 45.0%, respectively). SlopePID should be used instead of PercentPID as a metric to evaluate acute pain relief on a 0 to 10 NRS.
authors.affiliation: Department of Emergency Medicine, Research Centre, Sacré-Coeur Hospital of Montreal, Montreal, QC, Canada Department of Emergency and Family Medicine, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada Center for Advanced Research in Sleep Medicine, Sacré-Coeur Hospital of Montreal, Montreal, QC, Canada Faculties of Dental Medicine and Medicine, Université de Montréal, Montreal, QC, Canada.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Chauny
authors.forename: Jean
authors.initials: J
authors.lastname: Paquet
authors.forename: Gilles
authors.initials: G
authors.lastname: Lavigne
authors.forename: Martin
authors.initials: M
authors.lastname: Marquis
authors.forename: Raoul
authors.initials: R
authors.lastname: Daoust
mesh_terms: D059787:Acute Pain / Q000628:therapy*; D000293:Adolescent; D000328:Adult; D015982:Bias; D015331:Cohort Studies; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059408:Pain Management / Q000379:methods*; D010147:Pain Measurement; D012372:ROC Curve; D016896:Treatment Outcome; D055815:Young Adult