title: Serum prostate-specific antigen hemodilution among obese men undergoing screening in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.
abstract: BACKGROUND
  Previous studies have shown an inverse relationship between prostate-specific antigen (PSA) concentration and body mass index (BMI). It has been recently proposed that this relationship may be explained by the larger plasma volume of obese men diluting a fixed amount of PSA (hemodilution effect). We examined this hypothesis in a cohort of men enrolled in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial.
  
  
  METHODS
  Of 38,349 men ages 55 to 74 years randomized in PLCO to receive annual PSA and digital rectal examination screening, 28,380 had a baseline PSA, complete demographic information, and no prostate cancer diagnosis within 6 years from baseline. Self-reported height and weight were used to calculate BMI and to estimate plasma volume. PSA mass was estimated as PSA concentration times plasma volume. Multivariable linear regression models were used to investigate the relationship between PSA concentration, plasma volume, PSA mass, and BMI.
  
  
  RESULTS
  PSA concentration significantly decreased with increasing BMI (P<0.001); mean PSA values were 1.27, 1.25, 1.18, and 1.07 ng/mL among normal (BMI, 18.5-25), overweight (BMI, 25-30), obese (BMI, 30-35), and morbidly obese (BMI, >35) men, respectively. However, plasma volume also increased with increasing BMI and PSA mass showed no association with BMI, with mean values of 3.78, 3.95, 3.97, and 3.82 microg across the four BMI categories (P=0.10).
  
  
  CONCLUSIONS
  This study confirms earlier findings that the inverse relationship between PSA concentration and BMI may be explained by a hemodilution effect. These findings could have implications for prostate cancer screening in large men.
authors.affiliation: Division of Urologic Surgery, Washington University School of Medicine, 4960 Children's Place, Campus Box 8242, St. Louis, MO 63110, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Grubb
authors.forename: Amanda
authors.initials: A
authors.lastname: Black
authors.forename: Grant
authors.initials: G
authors.lastname: Izmirlian
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Hickey
authors.forename: Paul F
authors.initials: PF
authors.lastname: Pinsky
authors.forename: Jerome E
authors.initials: JE
authors.lastname: Mabie
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Riley
authors.forename: Lawrence R
authors.initials: LR
authors.lastname: Ragard
authors.forename: Philip C
authors.initials: PC
authors.lastname: Prorok
authors.forename: Christine D
authors.initials: CD
authors.lastname: Berg
authors.forename: E David
authors.initials: ED
authors.lastname: Crawford
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Church
authors.forename: Gerald L
authors.initials: GL
authors.lastname: Andriole
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D015992:Body Mass Index; D016009:Chi-Square Distribution; D006438:Hemodilution; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000150:complications; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood*; D011795:Surveys and Questionnaires
chemical_list: D017430:Prostate-Specific Antigen