Development and validation of the ABC pain scale for healthy full-term babies

Aim: We developed and validated a pain scale (ABC scale) for term babies based on acoustic features of crying. Methods: The scale consisted of three different cry parameters: (a) pitch of the first cry; (b) rhythmicity of the crying bout; (c) constancy of crying intensity. These parameters were previously found to distinguish between medium and high levels of pain measured by spectral analysis of crying. We validated the scale using healthy term babies undergoing routine heel prick. Concurrent validity was assessed comparing pain values obtained with our scale with those obtained with another pain scale; this relationship was also used to assess the sensitivity of the scale. To assess specificity we compared the ABC scores during a painful event (heel prick) with two non-painful events (preliminary phase of prick in the same group of babies, and heel prick with analgesia in another group). Results: Specificity: (a) analgesic/non-analgesic comparison, p<0.0001; (b) pain/sham comparison, p<0.0001). Sensitivity: a high correlation between scores of the ABC scale and the Douleur Aigue du Nouveau-Ne scale indicates good sensitivity. Concurrent validity: Spearman rho=0.91. Internal consistency: Cronbach's alpha=0.76. Inter-rater reliability: Cohen's kappa for multiple raters=0.83. Intra-rater reliability: Cohen's kappa=0.85. Practicality: All nurses who used it scored the scale as "good". Conclusion: The ABC scale proved to be simple and reliable for assessing pain in healthy, non-intubated term newborns.