New opiate and crack-cocaine users: characteristics and trends 12 
 
 
Table 3: Descriptive statistics for the DIP positive opiate-only/positive-for-both tests in which 
an individual can be identified with a PNC number.  
 
The age and year of birth distributions are also similar and are shown in the Appendix. Thus, for 
the majority of the analysis that follows, tests with no PNC number were excluded.10  
The charts and tables above use data from all positive tests, so will include cases where the 
same individual has tested positively on more than one occasion. The following data look just at 
the first test for each individual testing positive for opiates-only or positive-for-both. 
Table 4: Descriptive statistics on first positive opiate-only/positive-for-both tests. 
First positive opiate/opiate+cocaine tests (unique individuals) 
Age Year of birth 
Number of tests  104,817 Number of tests 104,817 
Mean 31 Mean 1977 
Median 30 Median 1977 
Mode 27 Mode 1980 
Minimum 18 Minimum 1960 
Maximum 53 Maximum 1995 
 
There were just over 100,000 unique individuals who tested positive for opiates-only or positive-
for-both between 2004 and 2013. The distribution of the 296,008 positive tests these individuals 
gave, shows that the vast majority (55%) were only tested once (see Figure 4), which is likely to 
be why the age statistics are quite similar between Table 3 and Table 4. However, within this 
 
10  Examining the data it is also clear that some areas recorded a higher proportion of cases without a PNC number than 
others. Thus excluding these cases further affects the variation in geographic coverage across time. See Appendix for more. 
All positive opiate/opiate+cocaine tests (including repeats) that were recorded on PNC; 
England 2004–2013 
Age Year of birth 
Number of tests  296,008 Number of tests 296,008 
Mean 32 Mean 1977 
Median 31 Median 1977 
Mode 28 Mode 1979 
Minimum 18 Minimum 1960 
Maximum 53 Maximum 1995