title: Seasonality of serum prostate-specific antigen levels: a population-based study.
abstract: OBJECTIVE
  The measurement of PSA serum levels is central to all early detection programs for prostate cancer. Although individual PSA values were known to fluctuate in the short and long term, the influence of insolation and seasons on PSA had not been addressed to date. To assert the relationship between total and free PSA and meteorological data in 8644 participants (55-70 years) in the French arm of the ERSPC study.
  
  
  METHODS
  Blood sample was taken at the local laboratory after informed consent and frozen sera were sent for central testing of total and free PSA. PSA measurement was performed within 7 days on the Access 1.0 automat with Hybritech reagents. Monthly meteorological data -- insolation, daily temperatures and rain precipitations -- were obtained from the local branches of the National Meteorology Agency.
  
  
  RESULTS
  Total PSA -- but not free PSA -- was correlated with insolation, that is the monthly accrual in hours of sunshine during which the intensity was higher than 120 Watt x m(-2) (r = 0.05 (95%CI: 0.03-0.07; p < 0.0001)) while no relationships were shown between insolation and percent-free PSA (free PSA divided by the total PSA). Interdependence between total PSA and insolation was also apparent with respect to the 3 ng/mL ERSPC cutoff for recommending biopsies (213.1 vs. 206.2 hours, p = 0.004). Such relationship was even more evident in summer when the tested participants more often had a PSA > 3 ng/mL (17.1% vs. 14.3%, p = 0.0006) than in the rest of the year, resulting in 23% more chances of being referred for biopsies (Odds ratio 1.23, 95%CI: 1.10-1.40).
  
  
  CONCLUSIONS
  Total PSA was shown to be strongly associated with insolation and seasons while the percent-free PSA was not influenced.
authors.affiliation: Laboratoire de Biologie, Centre Hospitalier Général Castres-Mazamet, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Salama
authors.forename: Olivier
authors.initials: O
authors.lastname: Noirot
authors.forename: Vincent
authors.initials: V
authors.lastname: Bataille
authors.forename: Sandra
authors.initials: S
authors.lastname: Malavaud
authors.forename: Xavier
authors.initials: X
authors.lastname: Rebillard
authors.forename: Arnauld
authors.initials: A
authors.lastname: Villers
authors.forename: Bernard
authors.initials: B
authors.lastname: Malavaud
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood; D001706:Biopsy; D005602:France / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D011159:Population Surveillance / Q000379:methods*; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000453:epidemiology / Q000473:pathology; D012621:Seasons; D014887:Weather
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen