Medicare's date of service rule is painfully complex, and has been complexified over the years since it was first promulgated.
In a nutshell, all tests on inpatient specimens are bundled, unless ordered by the physician 14 days after the day of hospital discharge.
Tests on outpatient specimens are also bundled, EXCEPT FOR exceptions. The exceptions are "molecular pathology tests" and ADLT tests.* These tests are billed to Medicare by the lab that performed them, be it hospital or freestanding lab.
Tests on non-hospital-associated tests are billed by the performing lab.
The point of this blog is to flag that CMS has a webpage devoted to the 14 day rule, with a number of links. Here.
What's new to me, CMS offers, via a Zip file, an Excel spreadsheet listing by code and name all of the 349 lab codes that are EXEMPTED from outpatient bundling rules. Get the most current version at the CMS webpage under "lab codes exception" zip file. I've also put the April 2020 version in the cloud here. Note it has two tabs, one a CPT code tab and one a Notes tab. The date of decision is listed for each code. Newest codes are at the bottom in red.
What's Bundled, What's Not - CMS Lists Differ
Most of the codes exempted are in the CPT 812xx 813xx 814xx 815xx code series - human DNA/RNA tests. 81479 and 81599 (unlisted codes) are on this list.
Interestingly, if you go to the April 2020 file of all CPT codes in the outpatient setting, a few additional codes are "Status A" that are not on the list of excepted lab codes offered on the DOS page. For example, 86631 86632, chlamydia antibody tests, are status A, whereas the hundreds of microbiology codes around them are bundled status Q4. Mystery to me. But these 86631/86632 lab tests codes that are excepted from bundling are not on the special CMS listing of lab codes excepted from bundling.
Also, I saw elsewhere (probably a transmittal) that novel COVID codes U0001, U0002, U0003, U0004 are unbundled (Status A), but they aren't listed on the special list of excepted codes.
U0001 U0002 are listed on the general outpatient list of all codes, as unbundled, Status A, however.
ADLT tests are a tiny group of tests designated as Advanced Diagnostic Laboratory Tests by CMS. They are always sole source tests and are covered by Medicare and are either MAAA tests or FDA approved sole source tests. Rules.