Tax Topic 151 means your return is under review. This can be done for various credit claims such as Earned Income Credit or any of the education tax breaks (this is not all inclusive). Your best bet it to wait until the IRS contacts you via letter which can take up to or more than 4 weeks for you to receive it.
Tax Topic 151 is the code referring to your right to appeal in this situation. Read more here: https://www.irs.gov/taxtopics/tc151