Hello, Welcome to Just Answer and thanks for your question. Which corticosteroid?
it usually takes 1-3 days, depending on which particular corticosteroid
Thanks for the additional information. None of the medications you are taking (oral or topical) will affect the results of an HIV test.
The length of time corticosteroids are in your system depends on which corticosteroid it is. There are short-, intermediate- and long-acting ones. Methylprednisolone is an intermediate-acting one and it has a half life of 18-36 hours. It is completely out of your system in a maximum of 10-11 days. In any event, it will not affect HIV testing even if you were still on it.
Nothing whatsoever will affect it.