def onset_candidate_dates
    dates = []
    dates << safe_call_chain(:disease_event, :disease_onset_date)
    dates << safe_call_chain(:disease_event, :date_diagnosed)
    collections = []
    test_dates = []
    self.labs.each do |l|
      l.lab_results.collect{|r| collections << r.collection_date}
      l.lab_results.collect{|r| test_dates << r.lab_test_date}
    end
    dates << collections.compact.sort
    dates << test_dates.compact.sort
    dates << self.first_reported_PH_date
    dates << self.event_onset_date
    dates << self.created_at.to_date unless self.created_at.nil?
    dates.flatten
  end