title: The relationship between central and peripheral oxytocin concentrations: a systematic review and meta-analysis protocol.
abstract: BACKGROUND
  Research examining the effects of oxytocin (OT) interventions on psychiatric, social-behavioral, and social-cognitive outcomes regularly collect peripheral levels of OT as markers of central bioavailability. Such inferences rest on the assumption that central and peripheral levels of OT are directly associated. However, conflicting evidence from coordinated sampling of central and peripheral OT question the validity of this assumption. The purpose of this meta-analysis is to evaluate the correlation between central and peripheral OT, as well as to account for potential heterogeneity in the literature.
  
  
  METHODS
  Studies that report coordinated sampling of central and peripheral OT in humans and animals will be identified. Research investigating concentrations in both basal states and after exogenous administration will be considered. PubMed and Embase databases will be searched, along with citation lists of retrieved articles. Peer-reviewed studies written in English published from 1971 onwards will be included in the meta-analysis. Data will be extracted from eligible studies for a random-effects meta-analysis. For each study, a summary effect size, heterogeneity, risk of bias, publication bias, and the effect of categorical and continuous moderator variables will be determined.
  
  
  CONCLUSIONS
  This systematic review and meta-analysis will identify and synthesize evidence to determine if there is an association between central and peripheral OT concentrations. If significant associations are observed, evidence would provide a rationale for future research to use peripheral measures as a proxy for central OT concentrations.
  
  
  BACKGROUND
  PROSPERO CRD42015027864.
authors.affiliation: NORMENT, KG Jebsen Centre for Psychosis Research, Division of Mental Health and Addiction, University of Oslo, Oslo University Hospital, Oslo, Norway.|Department of Psychology, University of Oslo, Oslo, Norway.
authors.forename: Mathias
authors.initials: M
authors.lastname: Valstad
authors.affiliation: Telethon Kids Institute, University of Western Australia, Perth, Australia.
authors.forename: Gail A
authors.initials: GA
authors.lastname: Alvares
authors.affiliation: NORMENT, KG Jebsen Centre for Psychosis Research, Division of Mental Health and Addiction, University of Oslo, Oslo University Hospital, Oslo, Norway.
authors.forename: Ole A
authors.initials: OA
authors.lastname: Andreassen
authors.affiliation: NORMENT, KG Jebsen Centre for Psychosis Research, Division of Mental Health and Addiction, University of Oslo, Oslo University Hospital, Oslo, Norway.|Department of Psychology, University of Oslo, Oslo, Norway.
authors.forename: Lars T
authors.initials: LT
authors.lastname: Westlye
authors.affiliation: NORMENT, KG Jebsen Centre for Psychosis Research, Division of Mental Health and Addiction, University of Oslo, Oslo University Hospital, Oslo, Norway. daniel.quintana@medisin.uio.no.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Quintana
mesh_terms: D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D010120:Oxytocics / Q000493:pharmacokinetics; D010121:Oxytocin / Q000097:blood* / Q000134:cerebrospinal fluid* / Q000493:pharmacokinetics; D011863:Radioimmunoassay; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry; D000078202:Systematic Reviews as Topic; D015201:Meta-Analysis as Topic
chemical_list: D010120:Oxytocics; D010121:Oxytocin
keywords: Cerebrospinal fluid concentration; ELISA; Meta-analysis; Oxytocin; Plasma concentration; Protocol; RIA; Systematic review