For a number of years, CMS has published giant Excel spreadsheets of "correct coding edits" and "medically unlikely edits" which give allowable units of thousands of CPT code services or show which codes cannot be used together (e.g. "appendectomy" cannot be supplemented by a code for "wound closure.")
There is also a text document in paragraph style with hundreds of concepts and rules that govern correct coding for Medicare. This "provider's manual" has now been updated for 2016, and as usually, new revisions are shown in festive holiday red. The whole kit and caboodle can be downloaded at this CMS web page, here. Look for "NCCI Policy Manual...2016 [ZIP]." For the chemistry and pathology section, see inside that ten document ZIP file or see just the pathology chapter in the cloud, here.