Organisations that carry out pre-employment medicals do so to determine a baseline per worker, and to determine whether the worker's status meets the health fitness requirements for the role. The annual monitoring would be to check for any changes in that baseline that could possibly be a result of exposure to health related hazards within the workplace. Any changes noted enables the employer to address the issues and review the hazard controls.
So, a common practice I've seen around exit medicals for workers who are leaving the organisation is that if the annual screening was not conducted in the previous 6 months, then an exit medical will be done. However for workers that have been exposed to more significant risk environments - it would be a recommendation for them to undergo an exit medical examination, irrespective of whether a screening was done in the previous 6 month period. The employer can therefore demonstrate that they have been responsible in ensuring worker health.....