A comparison of two measures of facial activity during pain in the newborn child.

Facial activity is strikingly visible in infants reacting to noxious events. Two measures that reduce this activity to composite events, the Neonatal Facial Coding System (NFCS) and the Facial Action Coding System (FACS), were used to examine facial expressions of 56 neonates responding to routine heel lancing for blood sampling purposes. The NFCS focuses upon a limited subset of all possible facial actions that had been identified previously as responsive to painful events, whereas the FACS is a comprehensive system that is inclusive of all facial actions. Descriptions of the facial expressions obtained from the two measurement systems were very similar, supporting the convergent validity of the shorter, more readily applied system. As well, the cluster of facial activity associated with pain in this sample, using either measure, was similar to the cluster of facial activity associated with pain in adults and other newborns, both full-term and preterm, providing construct validity for the position that the face encodes painful distress in infants and adults.