Q. How do I cite AHRQ in APA format?

In your question you mentioned who you want to cite, but not what you want to cite - their website, a publication by the AHRQ, etc - so I can only partially answer your question.

I am assuming it would be a webpage. In that case APA has a basic form - author | date | title of page | URL retrieval statement.

Unless you see the specific name of an individual cited as the author of information you can assume it is a corporate author, in this case the Agency for Healthcare Research and Quality.

Your citation would look like this (with you substituting your information for my made-up information).

Agency for Healthcare Research and Quality. (2017, June 5). Really interesting stuff. Retrieved 

     from https://www.ahrq.gov/reallyinterestingstuff.html