title: Validation of dual energy X-ray absorptiometry measures of abdominal fat by comparison with magnetic resonance imaging in an Indian population.
abstract: OBJECTIVE
  Abdominal adiposity is an important risk factor for diabetes and cardiovascular disease in Indians. Dual energy X-ray absorptiometry (DXA) can be used to determine abdominal fat depots, being more accessible and less costly than gold standard measures such as magnetic resonance imaging (MRI). DXA has not been fully validated for use in South Asians. Here, we determined the accuracy of DXA for measurement of abdominal fat in an Indian population by comparison with MRI.
  
  
  METHODS
  146 males and females (age range 18-74, BMI range 15-46 kg/m(2)) from Hyderabad, India underwent whole body DXA scans on a Hologic Discovery A scanner, from which fat mass in two abdominal regions was calculated, from the L1 to L4 vertebrae (L1L4) and from the L2 to L4 vertebrae (L2L4). Abdominal MRI scans (axial T1-weighted spin echo images) were taken, from which adipose tissue volumes were calculated for the same regions.
  
  
  RESULTS
  Intra-class correlation coefficients between DXA and MRI measures of abdominal fat were high (0.98 for both regions). Although at the level of the individual, differences between DXA and MRI could be large (95% of DXA measures were between 0.8 and 1.4 times MRI measures), at the sample level, DXA only slightly overestimated MRI measures of abdominal fat mass (mean difference in L1L4 region: 2% (95% CI:0%, 5%), mean difference in L2L4 region:4% (95% CI: 1%, 7%)). There was evidence of a proportional bias in the association between DXA and MRI (correlation between difference and mean -0.3), with overestimation by DXA greater in individuals with less abdominal fat (mean bias in leaner half of sample was 6% for L1L4 (95%CI: 2, 11%) and 7% for L2L4 (95% CI:3,12%).
  
  
  CONCLUSIONS
  DXA measures of abdominal fat are suitable for use in Indian populations and provide a good indication of abdominal adiposity at the population level.
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom. amy.taylor@bristol.ac.uk
authors.forename: Amy E
authors.initials: AE
authors.lastname: Taylor
authors.forename: Hannah
authors.initials: H
authors.lastname: Kuper
authors.forename: Ravi D
authors.initials: RD
authors.lastname: Varma
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Wells
authors.forename: Jimmy D
authors.initials: JD
authors.lastname: Bell
authors.forename: K
authors.initials: K
authors.lastname: V Radhakrishna
authors.forename: Bharati
authors.initials: B
authors.lastname: Kulkarni
authors.forename: Sanjay
authors.initials: S
authors.lastname: Kinra
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Timpson
authors.forename: Shah
authors.initials: S
authors.lastname: Ebrahim
authors.forename: George Davey
authors.initials: GD
authors.lastname: Smith
authors.forename: Yoav
authors.initials: Y
authors.lastname: Ben-Shlomo
mesh_terms: D050153:Abdominal Fat / Q000000981:diagnostic imaging / Q000473:pathology*; D015502:Absorptiometry, Photon / Q000379:methods*; D000273:Adipose Tissue / Q000000981:diagnostic imaging / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D001823:Body Composition; D015992:Body Mass Index; D002138:Calibration; D005260:Female; D063426:Human Migration; D006801:Humans; D007194:India; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D051598:Whole Body Imaging / Q000379:methods