title: Reliability of self, parental, and researcher measurements of head circumference.
abstract: BACKGROUND
  The measurement of head circumference (HC) is widely used in clinical and research settings as a proxy of neural growth. Although it could aid data collection, no studies have explored either the reliability of adult self-measurements or parental measurements of young children. This study therefore aimed to examine whether adult self and parental measurement of HC constitute reliable data.
  
  
  RESULTS
  A total of 57 adults (32 male) were asked to measure their HC twice following written instructions (adult self-measurement). These measures were compared to those of a researcher independently measuring the same participant's HC twice. Additionally, mothers of 25 children (17 male) were also asked to measure their child's HC (parental measure), and again this was compared to researcher measurements of the child's HC. The intraclass correlation coefficient between adult self- and researcher measurement was 0.84 and between parent and researcher measurement was 0.99. The technical error of measurement was also acceptable, within the range of a skilled anthropometrist.
  
  
  CONCLUSIONS
  The high degree of agreement between researcher and adult self-measurement/parental measurement of HC demonstrates that these different assessors produce similarly reliable and reproducible data. This suggests adult self- and parental measurements can reliably be used for data collection to enable valid large-scale developmental and clinical studies of HC.
authors.affiliation: Department of Psychiatry, Autism Research Centre, University of Cambridge, Cambridge, UK. jillian.sullivan@cantab.net.
authors.forename: Jillian C
authors.initials: JC
authors.lastname: Sullivan
authors.forename: Teresa
authors.initials: T
authors.lastname: Tavassoli
authors.forename: Kimberly
authors.initials: K
authors.lastname: Armstrong
authors.forename: Simon
authors.initials: S
authors.lastname: Baron-Cohen
authors.forename: Ayla
authors.initials: A
authors.lastname: Humphrey