There is a need to identify a primary measure of infant
pain that can be used to assess
pain in infants undergoing
vaccine injections in order to facilitate
vaccine outcomes research. The aim of the present study was to determine the reliability, validity and practicality of 3 measures of
acute pain in infants; the Modified Behavioural
Pain Scale (MBPS), Neonatal Infant
Pain Scale (
NIPS), and Face Legs Activity Cry Consolability Scale (FLACC). Five raters rated
pain from videotapes in 120 infants aged 2-6 months undergoing
vaccine injections that participated in a randomized controlled trial designed to compare
pain responses between two
vaccines, DPTaP-Hib vaccine and PCV
vaccine. Inter-rater reliability coefficients for baseline and
vaccine injections were all greater than 0.85. Cronbach's alpha ranged from 0.83 to 0.94. Construct validity was demonstrated for all measures by
vaccine injection scores that were higher (p<0.001) than baseline scores and by PCV scores that were higher than DPTaP-Hib scores. Concurrent validity was demonstrated by bi-variate correlation coefficients that ranged from 0.84 to 0.92. Intra-rater reliability coefficients for scores obtained after a single viewing (simulating real time assessment) versus multiple viewings were ≥ 0.96. All measures demonstrated a significant difference in
pain scores between the more painful (PCV) and less painful (DPTaP-Hib) vaccine for scores obtained after a single viewing. The majority of raters (4 out of 5) preferred the MBPS. Together, these results provide preliminary support for the MBPS as the primary outcome of
pain during
vaccine injections in infants.