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

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.