title: Assessing skin pigmentation in epidemiological studies: the reliability of measurements under different conditions.
abstract: OBJECTIVE
  Different devices are used for the non-invasive measurement of (constitutive) skin pigmentation in (epidemiological) studies. Reproducibility of measurements with the Chromameter (CM, model CR 300, Minolta, Osaka) and the Reflectometer (RM, Courage & Khazaka, Cologne) has not yet been examined in detail and was addressed in a set of four experiments and studies respectively.
  
  
  METHODS
  Regarding the CM, the Y value of the Yxy CIE 1931 colour system was utilized, representing lightness in this colour space, while the RM measured reflectance at 660 nm with a small bandwidth of 20 nm. Both devices measure reflectance on a scale from 0 to 100%, however, in different wavelength ranges. Between 3 and 20 repetitions were performed on standard grey scales and different sets of human volunteers, including RM measurements in a large epidemiological field study.
  
  
  RESULTS
  While the coefficient of variation (V) increases and the intraclass correlation coefficient decreases from controlled laboratory to field conditions, reproducibility remained in a range considered acceptable, if adequate study conditions were maintained. In a direct comparison on human skin, V of the RM was significantly smaller than that of the CM.
  
  
  CONCLUSIONS
  Both devices can be used confidently in field studies; however, based on considerations of skin optics and in view of slightly lesser variability, the RM may be preferable.
authors.affiliation: Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen, Erlangen, Germany. wolfgang.uter@imbe.med.uni-erlangen.de
authors.forename: W
authors.initials: W
authors.lastname: Uter
authors.forename: M
authors.initials: M
authors.lastname: Benz
authors.forename: A
authors.initials: A
authors.lastname: Mayr
authors.forename: O
authors.initials: O
authors.lastname: Gefeller
authors.forename: A
authors.initials: A
authors.lastname: Pfahlberg
mesh_terms: D000328:Adult; D000368:Aged; D003124:Colorimetry / Q000295:instrumentation*; D016021:Epidemiologic Studies; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010783:Photometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012880:Skin Pigmentation / Q000502:physiology*; D055815:Young Adult