The Psychometric Properties of the MBPS Scale Used to Assess Procedural Pain

The Modified Behavioral Pain Scale (MBPS) was designed to assess procedural pain in infants and is considered valid for assessing immunization pain. The aim of this study was to assess the practical and psychometric properties of the MBPS when applied to other commonly performed procedures. Twenty-six clinicians independently applied the MBPS scale to segments of video collected from 100 infants and children aged 6 to 42 months undergoing 1 of 4 procedures in the emergency department. Positive correlation between MBPS and Visual Analogue Scale observer applied (VASobs) pain (r = .74) was shown and inter- and intrarater reliability coefficients were high (.87 and .89, respectively). Construct validity was shown by scale responsiveness to painful stimuli (4.6 times increase in scores across phases) and the capacity of the scale to distinguish between painful versus nonpainful procedures (P < .001). However, mean baseline scores for procedures were not 0 (likely a function of item descriptors for a "0" score) and the mean difference increased across phases for children with baseline scores >3, which was much lower than for children with scores <3 (P = .0001). Finally, 28% of scores changed after the second viewing of a video segment. The MBPS appears reliable and sensitive to procedural pain when applied by clinicians. Results question the capacity of the scale to differentiate between pain- and nonpain-related distress, the feasibility of this scale, and the appropriateness of item descriptors for medical procedures.

This article presents the psychometric and practical properties of the MBPS applied to assess procedural pain. Identification of a suitable scale for this purpose will support improved pain management in infants and young children who undergo painful procedures.