The evaluation of change in pain intensity: a comparison of the P4 and single-item numeric pain rating scales

J Orthop Sports Phys Ther. 2004 Apr;34(4):187-93. doi: 10.2519/jospt.2004.34.4.187.


Study design: Prospective observation study.

Objectives: To compare the test-retest reliability and longitudinal validity (sensitivity to change) of 2 single-item numeric pain rating scales (NPRSs) with a 4-item pain intensity measure (P4).

Background: Pain is a frequent outcome measure for patients seen in physical therapy; however, the error associated with efficient pain measures, such as the single-item NPRS, is greater than for self-report measures of functional status. Initial evaluation of the P4 suggests that it is more reliable and sensitive to change than the NPRS.

Methods and measures: Two single-item NPRSs and the P4 were administered on 3 occasions--initial visit (n = 220), within 72 hours of baseline (n = 213), and 12 days following baseline assessment (n = 183)--to patients with musculoskeletal problems receiving physical therapy. Reliability was assessed using a type 2,1 intraclass correlation coefficient. Longitudinal validity was assessed by correlating the measures' change scores with a retrospective rating of change that included patients' and clinicians' perspectives.

Results: The test-retest reliability and longitudinal validity of the P4 were significantly greater (P1<.05) than both single-item NPRSs. Minimal detectable change of the P4 at the 90% confidence level was estimated to be a change of 22% of the scale range (9 points) compared to 27.3% (3 points) and 31.8% (3.5 points) for the 2-day NPRS and 24-hour NPRS, respectively.

Conclusions: The findings of this study suggest the P4 is more adept at assessing change in pain intensity than popular versions of single-item NPRSs.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cohort Studies
  • Female
  • Health Status Indicators*
  • Humans
  • Male
  • Middle Aged
  • Musculoskeletal Diseases / diagnosis
  • Musculoskeletal Diseases / rehabilitation
  • Pain / diagnosis*
  • Pain / epidemiology
  • Pain / rehabilitation
  • Pain Measurement / methods*
  • Prospective Studies
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Severity of Illness Index
  • Surveys and Questionnaires