Relationship between prostate-specific antigen and hematocrit: does hemodilution lead to lower PSA concentrations in men with a higher body mass index?

OBJECTIVES

To examine whether a lower hematocrit was associated with a lower prostate-specific antigen (PSA), when stratifying by body mass index (BMI) in healthy men. PSA test is widely used in screening for prostate cancer. Many studies have found that PSA levels inversely correlate with BMI. It remains unclear whether hemodilution causes this inverse relationship.

METHODS

We investigated 19,367 men who visited a hospital for a routine health checkup in 2007. We obtained information on age, BMI, PSA, hematocrit, and smoking status. BMI was categorized as < 18.5, 18.5-22.0, 22.0-25.0, 25.0-30.0, and > or = 30.0 kg/m(2).

RESULTS

In all subjects, older age and lower BMI were weakly correlated with a higher PSA (r = 0.20, P <.001 and r = -0.05, P <.001, respectively). A multiple regression model for predicting PSA was constructed using age, current smoking status, and hematocrit for each BMI category. After controlling for age and smoking, PSA increased significantly with increasing hematocrit in participants with BMIs of 18.5-30 kg/m(2) (all P <.001). For example, in men with a BMI of 22-25 kg/m(2), slight increases (1.4% increase; 95% confidence interval, 1.0%-1.9%) were observed in PSA with a 1-unit increase in hematocrit.

CONCLUSIONS

In healthy men with a BMI of 18.5-30 kg/m(2), a lower hematocrit was significantly associated with a lower PSA. Hemodilution may explain the lower PSA levels observed in men with a higher BMI, resulting in an inverse relationship between BMI and PSA.