title: Subcutaneous adipose tissue thickness in adults - correlation with BMI and recommendations for pen needle lengths for subcutaneous self-injection.
abstract: OBJECTIVE
  One of the aims of a subcutaneous (SC) injection is to avoid intradermal or intramuscular injections. Pen systems are an alternative solution to single-use syringes and have become standard for example diabetes therapy. Shorter and smaller needles minimize pain and the risk of intramuscular injections. The thickness of subcutaneous adipose tissue (SCAT) varies with position and with body mass index (BMI). The aim of this study was the creation of a map of SCAT thickness at typical spots for SC self-injection.
  
  
  METHODS
  MRI scans of 116 prospectively enroled volunteers (56 men and 60 women) were analysed. SCAT thickness was determined at 17 spots over the abdominal wall, left thigh, buttocks and upper arm, typical sites for subcutaneous self-injection. SCAT thicknesses were correlated with BMI and waist-to-hip ratio (WHR), and a linear curve fit was performed. The best fitting linear functions for the prediction of the SCAT thickness dependent on BMI and WHR were derived.
  
  
  RESULTS
  Correlations between SCAT and BMI were higher (0·67-0·21) than with WHR (-0·67 to 0·09). In women, correlation coefficients between SCAT data at the abdomen and BMI/WHR were higher than in men. On the other hand, data showed better correlations at the extremities in men.
  
  
  CONCLUSIONS
  The data, with correlation between BMI and fat thickness at different injection sites in relation to gender, provide guidance in selecting an adequate pen needle length for deep and safe subcutaneous self-injection. WHR was a much weaker predictor when compared to BMI.
authors.affiliation: Department of Radiology, Diagnostic and Interventional Neuroradiology, University Hospital Tübingen, Hoppe-Seyler-Straße, Tübingen, Germany. Burkhard.ludescher@med.uni-tuebingen.de
authors.forename: Burkhard
authors.initials: B
authors.lastname: Ludescher
authors.forename: Marc
authors.initials: M
authors.lastname: Rommel
authors.forename: Tobias
authors.initials: T
authors.lastname: Willmer
authors.forename: Andreas
authors.initials: A
authors.lastname: Fritsche
authors.forename: Fritz
authors.initials: F
authors.lastname: Schick
authors.forename: Juergen
authors.initials: J
authors.lastname: Machann
mesh_terms: D000328:Adult; D001823:Body Composition; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007279:Injections, Subcutaneous / Q000295:instrumentation; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009339:Needles; D009929:Organ Size; D017410:Practice Guidelines as Topic; D012646:Self Administration / Q000295:instrumentation; D050151:Subcutaneous Fat / Q000473:pathology*; D049629:Waist-Hip Ratio; D051598:Whole Body Imaging