Comparative evaluations of single-item pain-intensity measures in cancer patients: Numeric rating scale vs. verbal rating scale

Abstract

Aims and objectives: To evaluate the psychometric quality of two single-item pain-intensity measures: the Numeric Rating Scale (NRS) and the Verbal Rating Scale (VRS).

Background: Measuring pain intensity is a vital step in initiating symptom management and evaluating the effectiveness of interventions with cancer patients. Single-item pain-intensity measures of the NRS and VRS format have been evaluated to be acceptable for use in clinical practice and research; however, evidence to choose one over the other, as a standardised pain-assessment format, is insufficient.

Design: Descriptive correlational study. The study was guided and reported following the STROBE guideline.

Methods: Data accrued at two time points during cancer treatment with a total of 249 patients treated in a Korean University Hospital. Two single-item measures were constructed to assess pain intensity over 1 week. The Brief Pain Inventory (BPI; pain intensity subscale and interference subscale) and the functional assessment of chronic illness therapy-fatigue were the criterion. Convergent and concurrent validity were tested with Pearson's correlations.

Results: In the convergent-validity evaluation of the cross-sectional association with the BPI, the NRS showed a much higher level of association than the VRS (0.81 versus 0.61). In convergent validity with a longitudinal association with the BPI, the NRS score change had a much higher level of association (0.61 versus 0.37). In concurrent-validity evaluation, the NRS and VRS showed similar levels of associations with fatigue (-0.48 versus -0.49). Yet, the NRS showed statistically higher levels of correlation with functional limitations than the VRS (0.55 versus 0.42), comparable to the concurrent validity of the BPI.

Conclusion: The NRS showed higher validity than VRS when assessing overall pain intensity over the past week.

Relevance to clinical nursing: Pain assessment is a vital role of nurses in caring for patients with cancer. Current study findings support the use of the single-item NRS pain measure to assess global pain intensity over the past week.

Keywords: assessment; cancer; fatigue; measures; oncology nursing; pain; psychometrics.