Final answer:
The occupational health nurse should instruct the employee to obtain a chest x-ray to confirm if they have active tuberculosis.
Step-by-step explanation:
The occupational health nurse in the factory should plan to instruct the employee who has a positive Mantoux tuberculin test to obtain a chest x-ray. This is because a positive Mantoux test indicates exposure to tuberculosis (TB), but it does not confirm an active infection. Chest radiographs are required to look for any signs of TB infection, such as Ghon complex formation. Therefore, getting a chest x-ray would help confirm whether the employee has active TB or not.