Q. How do I cite a guideline from the National Guideline Clearinghouse in APA format for a reference list?

I don't actually have eyes on the guideline you are going to cite, but looking at the NCC webpage, I would cite a guideline as a webpage.

The basic form is:  author | date | title | retrieval statement

As it states in its title the NCC is a clearinghouse, meaning each guide could have a different author. I chose one at random to use as an examples - 

https://www.guideline.gov/summaries/summary/48754/myocardial-infarction-acute-early-rule-out-using-highsensitivity-troponin-tests-elecsys-troponin-t-highsensitive-architect-stat-high-sensitive-troponini-and-accutni-3-assays

A citation would look like this -

National Institute for Health Care Excellence. (2014, October). Myocardial infarction (acute): Early rule 
                out using high-sensitivity troponin tests (Elecsys Troponin T high-sensitive, ARCHITECT STAT High 
                Sensitive Troponin-I and AccuTnI+3 assays). Retrieved from https://www.guideline.gov/
                summaries/summary/48754/myocardial-infarction-acute-early-rule-out-using-highsensitivity-
                troponin-tests-elecsys-troponin-t-highsensitive-architect-stat-high-sensitive-troponini-and-
                accutni-3-assays

The software I use to answer these questions sometimes blows out the formatting in my email reply, so make sure you double-space the citation. You will get a better view if you follow the link in the email to where the question is logged in AskUs.