title: Gender disparity in BMD conversion: a comparison between Lunar and Hologic densitometers.
abstract: Female-derived inter-conversion and standardised BMD equations at the lumbar spine and hip have not been validated in men. This study of 110 male subjects scanned on Hologic and Lunar densitometers demonstrates that published equations may not applicable to men at the lumbar spine. Male inter-conversion equations have also been derived.
  
  
  OBJECTIVE
  Currently, available equations for inter-manufacturer conversion of bone mineral density (BMD) and calculation of standardised BMD (sBMD) are used in both males and females, despite being derived and validated only in women. Our aim was to test the validity of the published equations in men.
  
  
  METHODS
  One hundred ten men underwent lumbar spine (L2-4), femoral neck (FN) and total hip (TH) dual X-ray absorptiometry (DXA) using Hologic and Lunar scanners. Hologic BMD was converted to Lunar using published equations derived from women for L2-4 and FN. Actual Lunar BMD (A-Lunar) was compared to converted (Lunar equivalent) Hologic BMD values (H-Lunar). sBMD was calculated separately using Hologic (sBMD-H) and Lunar BMD (sBMD-L) at L2-4, FN and TH. Conversion equations in men for Hologic to Lunar BMD were derived using Deming regression analysis.
  
  
  RESULTS
  There was a strong linear correlation between Lunar and Hologic BMD at all skeletal sites. A-Lunar BMD was however significantly higher than derived H-Lunar BMD (p < 0.001) at L2-L4 (mean difference, 0.07 g/cm(2)). There was no significant difference at the FN (mean difference, 0.01 g/cm(2)). sBMD-L at the spine was significantly higher than sBMD-H (mean difference, 0.06 g/cm(2), p < 0.001), whilst there was little difference at the FN and TH (mean difference, 0.01 g/cm(2)).
  
  
  CONCLUSIONS
  Published conversion equations for Lunar BMD to Hologic BMD, and formulae for lumbar spine sBMD, derived in women may not be applicable to men.
authors.affiliation: Bone Research Program, ANZAC Research Institute, The University of Sydney, Sydney, Australia.
authors.forename: Kirtan
authors.initials: K
authors.lastname: Ganda
authors.forename: Tuan V
authors.initials: TV
authors.lastname: Nguyen
authors.forename: Nicholas
authors.initials: N
authors.lastname: Pocock
mesh_terms: D015502:Absorptiometry, Photon / Q000295:instrumentation / Q000592:standards*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D005272:Femur Neck / Q000000981:diagnostic imaging; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D012737:Sex Factors; D055815:Young Adult