text: Note: as a guide to the OCU population, this chart is left-truncated as DIP tests are not given to under-18s. 
  
  The above statistics include tests in which no Police National Computer (PNC) number was 
  recorded for an individual. This number is needed to identify an individual and hence to check 
  whether future tests are further tests by that individual or represent a new individual testing 
  positive. Excluding tests in which no PNC number was recorded makes little difference to the 
  descriptive statistics, see Table 3 below. 