CO-11: the diagnosis is inconsistent with the procedure

Claim adjustment reason code 11 says the diagnosis is inconsistent with the procedure. The group code CO means the amount is the provider's responsibility, so the patient can't be billed for it.

It is close to CO-50, but not the same. CO-50 says the service wasn't medically necessary. CO-11 says the diagnosis on the line doesn't fit the procedure on that line at all, which is more often a coding or claim-building problem than a clinical one.

• The wrong diagnosis is pointed to. On a professional claim, each service line points to one or more of the claim's diagnoses. If the line for a knee injection points to a back-pain diagnosis, the line is inconsistent even when the right diagnosis is elsewhere on the claim.
• The diagnosis isn't specific enough. A coverage policy may list specific codes, and an unspecified code is treated as not matching.
• Laterality doesn't match. A right-side diagnosis on a line billed with a left-side modifier (LT), or the reverse.
• The diagnosis isn't on the coverage policy's list for that procedure in your contractor's region.

• Check the diagnosis pointer on every line, not just the diagnoses on the claim.
• Code to the most specific diagnosis the note supports, including laterality.
• Match modifiers to the diagnosis: side, site and any modifier the policy requires.
• Check the procedure against your contractor's coverage policy where one exists. Your state decides which contractor applies: see the contractor by state table.

• Look at the line, not the claim. Find which diagnosis the denied line pointed to, and whether a better one was documented.
• If it was a pointer, specificity or laterality error, it is usually a correction rather than an appeal. For Medicare Part B, clerical errors like these are generally fixed through your contractor's reopening process.
• If the diagnosis was right, and the payer still says it is inconsistent, request a redetermination with the clinical note that links the diagnosis to the service.

• CO-50: not deemed medically necessary.
• CO-167: the diagnosis is not covered.

This guide is general information, not legal or billing advice. Always check the current policy for your contractor and your payer's own rules.