Systematic review of terminology, definitions, and eligibility criteria in trials of neonatal encephalopathy, hypoxic-ischemic encephalopathy, and perinatal asphyxia

BACKGROUND: Appropriate terminology and definitions of neonatal encephalopathy (NE), hypoxic-ischemic encephalopathy (HIE), and perinatal asphyxia (PA) remain controversial. Participant criteria used in therapeutic hypothermia (TH) trials are frequently used as case definitions for NE/HIE/PA but studies are inconsistent. This review aims to assess variations in terminology and case participant criteria between trials for NE/HIE/PA. METHODS: Search strategy retrieved articles from databases (Embase, MEDLINE, CENTRAL, CDSR and WHO) for randomized controlled trials (RCTs) of interventions for NE/HIE/PA using any definition for NE/HIE/PA. Outcomes were a description of the terminology, definitions, and participant criteria. Two reviewers independently screened results. Qualitative results were synthesized in a narrative summary. RESULTS: The search provided 6768 results. 67 were included in the qualitative synthesis. HIE was the most frequently used term (56/67). NE was the least frequent (16/67). Some of the common inclusion criteria were Apgar scores (63/67), metabolic acidosis (58/67), and reduced level of consciousness (57/67). Most frequently employed exclusion criteria were prematurity (63/67), major congenital abnormalities (62/67), and identification beyond 6 h from birth (62/67). DISCUSSION: This review identified variations in terminology and in-trial participant criteria between studies. These results will inform a consensus process for developing a definition and case definition of NE/HIE/PA. IMPACT: Our article demonstrated significant variations in the terminology used to describe the condition of NE/HIE/PA, which demonstrates a need for more consistent definitions in terminology. A broad but meaningful definition of the condition would provide an inclusive approach while permitting subclassifications within the condition, and permitting comparisons and benchmarking across different settings. Developing consistency across these areas, as far as possible, would allow improved interpretation of interventions on long-term prognosis and greater generalizability of trial results.