Where Lab Test OPPS Packaging Comes from (CFR)

 The actual rules stem from the definition of bundled hospital services in one regulation, and the complex 14 day rule in another regulation.

Pretty bizarrely, 42 CFR 419.22(l) [el] excludes clinical diagnostic laboratory tests from payment under the APC system or by APCs.    (*)  

Except as provided by 419.2(b)(17), which does the opposite and bundles most lab tests as packaged costs in the APC system (!!!!!).   That's a cause for whiplash.

And - Further details of the bundling and unbundling occur as a result of the date of service rule aka 14 day rule.  42 CFR 414.510.  For example, this sets a separate date of service for "molecular pathology" tests.

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(*) This means CMS will not take CPT lab codes and crosswalk them to payment by linking them to an APC.   CMS does do exactly this, for some other products.