CO-186 denial code
Level of care change adjustment
How to fix it
Confirm the level of care billed matches the record and appeal where documentation supports the higher level.
How to prevent it
Document level-of-care changes contemporaneously so the billed level is supportable.
In practice
A patient is admitted as an inpatient. The payer reviews and determines observation status was appropriate, adjusting payment to that level under CO-186.
Level of care determinations turn on documented clinical criteria: the expected length of stay, the intensity of service required, and the severity of illness recorded at the time of the decision.
The appeal succeeds where the record shows those criteria were met at admission, documented contemporaneously by the admitting physician. It fails where the note records the decision without recording the reasoning behind it.
What sits behind it
Payers apply published screening criteria to these reviews, and the same criteria are available to providers. Writing the admission note against the criteria the reviewer will use is considerably more effective than writing it and hoping, and it takes no additional time.
The financial gap between levels is large, which is why these reviews happen. Inpatient and observation payment differ substantially, and the patient's cost sharing differs too, so a downgrade affects the patient's bill as well as the facility's payment.
Timing is decisive in the record. A physician's judgement documented at the point of admission carries weight; the same judgement asserted in an appeal months later, without contemporaneous support, generally does not survive review.
Related codes
Terms used here — Medical Necessity · Appeal · E/M Coding
How we handle it — Denial Management · Practice Analytics · Revenue Cycle Management
Primary sources
The rules behind CO-186, at the bodies that publish them.
- Medicare Coverage Database (LCD/NCD) (opens in a new tab)
Centers for Medicare & Medicaid Services — Searchable national and local coverage determinations. The direct answer to whether a diagnosis supports medical necessity for a given procedure.
- Medicare Benefit Policy Manual (opens in a new tab)
Centers for Medicare & Medicaid Services — What Medicare covers and under what conditions, as distinct from how a claim is processed. The starting point for any coverage or medical necessity question.
- Advance Beneficiary Notice of Noncoverage (ABN) (opens in a new tab)
Centers for Medicare & Medicaid Services — The form and the rules for issuing it. Whether a non-covered service can be billed to the patient usually turns on whether a valid ABN was obtained beforehand.
Looking for a different code? Search all 190 CARC and RARC codes
Questions about CO-186
Contemporaneous documentation showing the clinical criteria were met at the time of the decision — expected length of stay, intensity of service, severity of illness. A judgement recorded at admission carries weight; the same judgement asserted later in an appeal usually does not.
Generally yes. Payers apply published screening criteria and providers can access them, which means the admission note can be written against the standard the reviewer will actually apply. That costs no extra time and materially improves the outcome.
Yes. Cost sharing differs between inpatient and observation status, sometimes substantially, so a downgrade changes the patient's bill as well as the facility's payment. Patients affected by a retrospective change frequently need an explanation they were never given at admission.
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