BACKGROUND

Several pain rating methods are used to quantify pain. Although these instruments have been extensively studied, their inter-agreement, especially in emergency department (ED) settings, has yet to be determined.

OBJECTIVE

This study was designed to assess the agreement between Visual Analog Scale (VAS), Color Analog Scale (CAS), and verbally administered Numeric Rating Scale (NRS) in the emergency setting.

METHODS

A sample of 150 adult patients presenting with acute pain to two EDs was recruited. Patients' pain severity at presentation, 30 and 60 min later was assessed using the three pain scales. The agreement between pain scales was assessed using Bland-Altman method and Spearman correlation. We described a composite measure to serve as the gold standard and to be compared with each score. Factor analysis was also performed to assess the underlying construct.

RESULTS

Spearman correlation coefficients between NRS and CAS, NRS and VAS, and CAS and VAS were 0.95, 0.94, and 0.94, respectively (p < 0.001). On a scale of 0 to 10, the 95% limits of agreement between the paired NRS and VAS, VAS and CAS, and CAS and NRS as measured by Bland-Altman method ranged from -2.0 to 2.6, from -2.7 to 2.0, and from -2.1 to 2.0, respectively. The Kaiser-Meyer-Oklin measure of sampling adequacy was 0.785 and Bartlett's test for sphericity was significant (p < 0.001).

CONCLUSIONS

The three pain scales were strongly correlated at all time periods. The findings suggest that NRS, CAS, and VAS can be interchangeably applied for acute pain measurement in adult patients.