title: Bioelectrical impedance vector distribution in the first year of life.
abstract: OBJECTIVE
  We assessed the bioelectrical impedance vector distribution in a sample of healthy infants in the first year of life, which is not available in literature.
  
  
  METHODS
  The study was conducted as a cross-sectional study in 153 healthy Caucasian infants (90 male and 63 female) younger than 1 y, born at full term, adequate for gestational age, free from chronic diseases or growth problems, and not feverish. Z scores for weight, length, cranial circumference, and body mass index for the study population were within the range of +/-1.5 standard deviations according to the Euro-Growth Study references. Concurrent anthropometrics (weight, length, and cranial circumference), body mass index, and bioelectrical impedance (resistance and reactance) measurements were made by the same operator. Whole-body (hand to foot) tetrapolar measurements were performed with a single-frequency (50 kHz), phase-sensitive impedance analyzer. The study population was subdivided into three classes of age for statistical analysis: 0 to 3.99 mo, 4 to 7.99 mo, and 8 to 11.99 mo. Using the bivariate normal distribution of resistance and reactance components standardized by the infant's length, the bivariate 95% confidence limits for the mean impedance vector separated by sex and age groups were calculated and plotted. Further, the bivariate 95%, 75%, and 50% tolerance intervals for individual vector measurements in the first year of life were plotted.
  
  
  RESULTS
  Resistance and reactance values often fluctuated during the first year of life, particularly as raw measurements (without normalization by subject's length). However, 95% confidence ellipses of mean vectors from the three age groups overlapped each other, as did confidence ellipses by sex for each age class, indicating no significant vector migration during the first year of life.
  
  
  CONCLUSIONS
  We obtained an estimate of mean impedance vector in a sample of healthy infants in the first year of life and calculated the bivariate values for an individual vector (95%, 75%, and 50% tolerance ellipses).
authors.affiliation: Department of Pediatrics, University of Turin, Regina Margherita Children Hospital, Piazza Polonia, 94-10126 Turin, Italy. savino@pediatria.unito.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Savino
authors.forename: Giulia
authors.initials: G
authors.lastname: Grasso
authors.forename: Francesco
authors.initials: F
authors.lastname: Cresi
authors.forename: Roberto
authors.initials: R
authors.lastname: Oggero
authors.forename: Leandra
authors.initials: L
authors.lastname: Silvestro
mesh_terms: D000886:Anthropometry; D001034:Apgar Score; D001823:Body Composition; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005260:Female; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012016:Reference Values