Age‐adjusted reference values for prostate‐specific antigen in a multi‐ethnic population

OBJECTIVE To establish age-adjusted reference values for prostate-specific antigen in an ethnically diverse population. METHODS Between 2009 and 2017, data were collected from all men aged 40-79 years, who had a prostate-specific antigen test in the northern region of New Zealand, where the prostate-specific antigen testing service is provided by a single community laboratory and using the same assay analyzer. Men known to have prostate cancer, who developed prostate cancer during the study period, who were treated with finasteride, or who had prostate-specific antigen levels above 20 ng/mL were excluded. Age-adjusted prostate-specific antigen reference values were calculated for each of the main ethnic groups in the country including: Māori (indigenous), Pacific, Asian and European. For every 5-year age interval, the 95th percentile of the log prostate-specific antigen distribution was used to define the upper limit of normal. RESULTS The study cohort included 215 132 apparently healthy men, with a median age and prostate-specific antigen concentration of 59 years and 0.9 ng/mL, respectively. Prostate-specific antigen levels for the entire cohort increased with age (Pearson correlation = 0.362, P < 0.001). This relationship was most prominent in Pacific men. Similarly, the upper reference limit for the entire cohort increased with age, from 1.60 ng/mL for men aged 40-44 years to 7.61 ng/mL for those aged 75-79 years. Significant ethnic differences were present within each interval, which was most apparent in the older age groups. CONCLUSION Ethnic differences in age-adjusted prostate-specific antigen reference values are present in New Zealand. These need to be considered when prostate-specific antigen results are being interpreted in clinical practice.