Discrepancies in Describing Pain: Is There Agreement Between Numeric Rating Scale Scores and Pain Reduction Percentage Reported by Patients with Musculoskeletal Pain After Corticosteroid Injection?

A new reproducibility index is developed and studied. This index is the correlation between the two readings that fall on the 45 degree line through the origin. It is simple to use and possesses desirable properties. The statistical properties of this estimate can be satisfactorily evaluated using an inverse hyperbolic tangent transformation. A Monte Carlo experiment with 5,000 runs was performed to confirm the estimate's validity. An application using actual data is given.

Patients' memories of painful medical procedures may influence their decisions about future treatments, yet memories are imperfect and susceptible to bias. We recorded in real-time the intensity of pain experienced by patients undergoing colonoscopy (n = 154) and lithotripsy (n = 133). We subsequently examined patients' retrospective evaluations of the total pain of the procedure, and related these evaluations to the real-time recording obtained during the experience. We found that individuals varied substantially in the total amount of pain they remembered. Patients' judgments of total pain were strongly correlated with the peak intensity of pain (P < 0.005) and with the intensity of pain recorded during the last 3 min of the procedure (P < 0.005). Despite substantial variation in the duration of the experience, lengthy procedures were not remembered as particularly aversive. We suggest that patients' memories of painful medical procedures largely reflect the intensity of pain at the worst part and at the final part of the experience.

An important issue that has yet to be resolved in pain measurement literature concerns the number of levels needed to assess self-reported pain intensity. An examination of treatment outcome literature shows a large variation in the number of levels used, from as few as 4 (e.g., 4-point Verbal Rating scales (VRS)) to as many as 101 (e.g., 101-point Numerical Rating scales (NRS)). The purpose of this study was to provide an empirically derived guideline for determining the number of levels needed. Chronic pain patients (n = 124) provided pre- and post-treatment measures of pain intensity using 101-point NRS for least, most, current, and average pain. The patients' responses to the measures were examined closely to determine the actual number of levels used. In addition, their responses to the 101-point scales were recorded to form 7 scales of varying levels (2- to 101-point scales). The sensitivity of the 7 recorded scales was examined. The results indicated that little information is lost if 101-point scales are coded as 11- or 21-point scales. Moreover, examination of the actual responses to the 101-point measure showed that almost all patients treated it as a 21-point scale by providing responses in multiples of 5 or 10, while a substantial number of patients treated it as an 11-point scale, providing responses in multiples of 10 only. The results suggest that 10- and 21-point scales provide sufficient levels of discrimination, in general, for chronic pain patients to describe pain intensity.