title: Performance of total testosterone measurement to predict free testosterone for the biochemical evaluation of male hypogonadism.
abstract: OBJECTIVE
  Guidelines recommend serum total testosterone measurement as the initial test to evaluate male hypogonadism, reserving free testosterone assessment for men with suspected sex hormone-binding globulin abnormalities or total testosterone near the lower limit of normal. We determined the performance of total testosterone measurement as a test to identify men with normal vs low free testosterone.
  
  
  METHODS
  We examined the electronic medical records of all 3,672 men evaluated for hypogonadism by a serum testosterone panel, including total testosterone, sex hormone-binding globulin, albumin and calculated free testosterone, from January 1, 1997 through December 31, 2007 in a network that serves veterans in Washington.
  
  
  RESULTS
  The sensitivity and specificity of low total testosterone (less than 280 ng/dl) to rule out and predict low calculated free testosterone was 91.0% and 73.7%, respectively. At thresholds of less than 350 and less than 400 ng/dl the sensitivity of total testosterone for low calculated free testosterone increased to 96.8% and 98.2%, and at thresholds of less than 150 and less than 200 ng/dl specificity increased to 98.9% and 92.6%, respectively.
  
  
  CONCLUSIONS
  Total testosterone between 280 and 350 ng/dl is not sensitive enough to reliably exclude hypogonadism. Total testosterone must exceed 350 to 400 ng/dl to reliably predict normal free testosterone. Except when levels are less than 150 ng/dl total testosterone measurement has low specificity for the biochemical diagnosis of hypogonadism.
authors.affiliation: Department of Medicine, University of Washington and Geriatric Research, Seattle, Washington 98195, USA. banawalt@medicine.washington.edu
authors.forename: Bradley D
authors.initials: BD
authors.lastname: Anawalt
authors.forename: James M
authors.initials: JM
authors.lastname: Hotaling
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Walsh
authors.forename: Alvin M
authors.initials: AM
authors.lastname: Matsumoto
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D007006:Hypogonadism / Q000097:blood* / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D013739:Testosterone / Q000097:blood*; D055815:Young Adult
chemical_list: D013739:Testosterone