[Pain assessment using the Facial Action Coding System. A systematic review].

Self-reporting is the most widely used pain measurement tool, although it may not be useful in patients with loss or deficit in communication skills. The aim of this paper was to undertake a systematic review of the literature of pain assessment through the Facial Action Coding System (FACS). The initial search found 4,335 references and, within the restriction «FACS», these were reduced to 40 (after exclusion of duplicates). Finally, only 26 articles meeting the inclusion criteria were included. Methodological quality was assessed using the GRADE system. Most patients were adults and elderly health conditions, or cognitive deficits and/or chronic pain. Our conclusion is that FACS is a reliable and objective tool in the detection and quantification of pain in all patients.