title: Reproducibility and day time bias correction of optoelectronic leg volumetry: a prospective cohort study.
abstract: BACKGROUND
  Leg edema is a common manifestation of various underlying pathologies. Reliable measurement tools are required to quantify edema and monitor therapeutic interventions. Aim of the present work was to investigate the reproducibility of optoelectronic leg volumetry over 3 weeks' time period and to eliminate daytime related within-individual variability.
  
  
  METHODS
  Optoelectronic leg volumetry was performed in 63 hairdressers (mean age 45 ± 16 years, 85.7% female) in standing position twice within a minute for each leg and repeated after 3 weeks. Both lower leg (legBD) and whole limb (limbBF) volumetry were analysed. Reproducibility was expressed as analytical and within-individual coefficients of variance (CVA, CVW), and as intra-class correlation coefficients (ICC).
  
  
  RESULTS
  A total of 492 leg volume measurements were analysed. Both legBD and limbBF volumetry were highly reproducible with CVA of 0.5% and 0.7%, respectively. Within-individual reproducibility of legBD and limbBF volumetry over a three weeks' period was high (CVW 1.3% for both; ICC 0.99 for both). At both visits, the second measurement revealed a significantly higher volume compared to the first measurement with a mean increase of 7.3 ml ± 14.1 (0.33% ± 0.58%) for legBD and 30.1 ml ± 48.5 ml (0.52% ± 0.79%) for limbBF volume. A significant linear correlation between absolute and relative leg volume differences and the difference of exact day time of measurement between the two study visits was found (P < .001). A therefore determined time-correction formula permitted further improvement of CVW.
  
  
  CONCLUSIONS
  Leg volume changes can be reliably assessed by optoelectronic leg volumetry at a single time point and over a 3 weeks' time period. However, volumetry results are biased by orthostatic and daytime-related volume changes. The bias for day-time related volume changes can be minimized by a time-correction formula.
authors.affiliation: Swiss Cardiovascular Center, Division of Clinical and Interventional Angiology Inselspital, University Hospital and University of Bern, Switzerland.
authors.forename: Rolf P
authors.initials: RP
authors.lastname: Engelberger
authors.forename: Claudia
authors.initials: C
authors.lastname: Blazek
authors.forename: Felix
authors.initials: F
authors.lastname: Amsler
authors.forename: Hong H
authors.initials: HH
authors.lastname: Keo
authors.forename: Frédéric
authors.initials: F
authors.lastname: Baumann
authors.forename: Werner
authors.initials: W
authors.lastname: Blättler
authors.forename: Iris
authors.initials: I
authors.lastname: Baumgartner
authors.forename: Torsten
authors.initials: T
authors.lastname: Willenberg
mesh_terms: D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D000886:Anthropometry / Q000295:instrumentation; D001505:Beauty Culture; D015982:Bias; D004487:Edema / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D006801:Humans; D007866:Leg / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000175:diagnosis* / Q000473:pathology; D009929:Organ Size; D011446:Prospective Studies; D015203:Reproducibility of Results; D012107:Research Design