Plasma volume changes affect prostate specific antigen in healthy men.

Abstract

PURPOSE: Several studies show that prostate specific antigen inversely correlates with body mass index. Hemodilution may be responsible for the lower prostate specific antigen in obese men. Hematocrit is the most popular indicator of plasma volume. We examined the effect of hematocrit changes on prostate specific antigen in healthy men during 2 years. We also investigated the association between prostate specific antigen and plasma volume changes based on combined changes in body weight and hematocrit. MATERIALS AND METHODS: We reviewed the records of 8,338 men who visited our institution for routine health assessments in 2005, 2006 and 2007. Using the combination of body weight and hematocrit changes in 1 year we defined hemodilution as weight gain with decreased hematocrit and hemoconcentration as weight loss with increased hematocrit. RESULTS: On multiple regression analysis controlling for patient age and weight change the hematocrit change was significantly associated positively with the prostate specific antigen change between 2005 and 2006 (1.2%/1 U), and between 2006 and 2007 (0.7%/1 U, each p <0.001). After controlling for age participants with hemoconcentration showed significantly greater prostate specific antigen changes than those with hemodilution, that is 6.1% between 2005 and 2006, and 4.8% between 2006 and 2007 (each p <0.001). CONCLUSIONS: Hematocrit change was positively associated with prostate specific antigen change. Compared to men with hemodilution significantly greater prostate specific antigen changes were observed in men with hemoconcentration. Thus, plasma volume may explain the inverse relationship between body mass index and prostate specific antigen.