OPRA denominator study

Data from the OPRA scheme is one of the most important sources of information for the estimated incidence of work-related ill health in the UK. An accurate incidence estimate requires valid data for both the numerator and the denominator.

About the survey

We have started a three-year rolling denominator survey to investigate the estimated number and industry of employees who are under the care of the occupational physicians in OPRA. We are incorporating this survey into the routine OPRA case reporting. Every year we will send out the denominator survey questionnaire to a third of the OPRA reporters together with their report cards, so each OPRA reporter should only need to fill in a questionnaire once in three years.

In OPRA, the numerator includes all newly diagnosed cases of work-related ill health seen by occupational physicians whilst the denominator includes all employees under the occupational health care of the OPRA physicians. The denominator survey carried out in April 2001 (J C McDonald, Occup. Med. 2002) collected, for the first time, very useful information about the approximate number of employees covered by the occupational health services of the OPRA participants and highlighted the disproportionate distribution of these services. However, the result from this survey was an estimate at one point in time, which is not compatible with the numerator information collected continuously in OPRA in more recent years. Moreover, we want to ensure that we are not 'double counting' the number of employees; therefore, we have added a few questions about 'group reporting'.

For further information on the April 2001 denominator survey, see:

Workforce coverage by GB occupational physicians and disease incidence rates
M. Carder, A. Money, S. Turner and R. Agius (PDF, 1.26MB)

The estimated workforce served by occupational physicians in the UK
Occup. Med. 2002; 52(7): 401-406
McDonald JC (PDF, 68 KB)


To assist you in completing the questionnaire and for more information about the industries we refer to, see: UK Standard Industrial Classification.


If you have any queries about the study itself or how to complete your questionnaire, please contact Melanie Carder:
+44 (0)161 275 5636

Many thanks to all our OPRA reporters for your continued support. We will provide you with further information about the results of the denominator study in due course.