Final answer:
Additional tests that should be done in patients with erythema nodosum include blood tests and imaging studies to identify the underlying cause and evaluate the inflammation.
Step-by-step explanation:
In patients with erythema nodosum, additional tests that should be done include blood tests and imaging studies. Blood tests can help identify the underlying cause of erythema nodosum, such as a streptococcal infection, tuberculosis, or sarcoidosis. Imaging studies like X-rays or CT scans may be used to evaluate the extent of the inflammation and check for any associated abnormalities.