The Record Must Tell the Story
Three out of every four sampled diagnoses didn’t hold up. That’s the headline from three new Office of Inspector General (OIG) audits of Medicare Advantage risk adjustment, and it should get the attention of every Clinical Documentation Improvement (CDI) specialist, coder, and compliance lead who touches a risk-adjusted claim.
In Medicare Advantage, a diagnosis isn’t just a description of the patient. It’s a payment input. When a high-severity code reaches the Centers for Medicare & Medicaid Services(CMS) without a medical record behind it, the plan is paid for a condition the documentation can’t prove. The OIG has been working through a series of these reviews, and the latest round, reported by ACDIS on October 15, 2026, shows the problem is far from solved.
What the OIG Found
Across three organizations, auditors found that 533 of 700 sampled enrollee-years lacked adequate medical-record support, with an estimated $202.2 million in overpayments for payment years 2020 and 2021.
| Organization | Enrollee-years Sampled | Unsupported | Unsupported Rate | Sampled Overpayment | Estimated Overpayment (PY 2020–2021) |
| HumanaChoice | 220 | 178 | 81% | $669,237 | at least $130.9M |
| UnitedHealthcare Benefits of Texas | 230 | 172 | 75% | $622,927 | at least $24.4M |
| UnitedHealthcare of Wisconsin | 250 | 183 | 73% | $722,280 | at least $46.9M |
Note: an “enrollee-year” pairs one person with one condition in one payment year. A single patient can count more than once if they carried several high-risk codes or the same code across both years.
The audits focused on ten condition groups that the OIG considers high risk for miscoding: acute stroke, acute myocardial infarction, sepsis, embolism, pressure ulcers, and five cancers (lung, breast, colon, ovarian, and prostate).
Within those groups, the failure rates were striking. In the Humana review, every one of the 20 sampled acute stroke cases came back unsupported. UnitedHealthcare of Wisconsin had a perfect miss on breast and colon cancer. In all three audits, several categories landed at 18 or 19 unsupported out of 20.
Why the Same Gaps Keep Showing Up
The conditions on the OIG’s list share a trait: they’re easy to code past their moment. That’s a pattern any experienced coder will recognize, even though the audit summaries don’t spell out the reason behind each miss.
Acute events that outlive their acuity. A stroke or heart attack is treated in the hospital. Months later, at a primary care or specialist visit, the patient has a history of that event, which is a different code with a different (often zero) risk-adjustment weight. When the acute code keeps riding forward on outpatient claims, the record won’t support it.
Cancer after active treatment ends. An active malignancy needs evidence of current treatment or disease. Once treatment is complete and there’s no evidence of disease, the right code is usually a personal history code. Problem lists that never get updated are a classic source of this error.
The keystroke problem. The OIG also flagged what it called potentially miskeyed diagnoses. In these cases, the record documented a condition, but the submitted code belonged to something unrelated. This showed up in 18 of 30 sampled enrollee-years in the Texas audit, 22 of 50 in Wisconsin, and 10 of 20 at Humana. Codes named in the reports include:
- C78.00, secondary malignant neoplasm of unspecified lung
- E78.00, pure hypercholesterolemia, unspecified
- G62.9, polyneuropathy, unspecified
- I62.9, nontraumatic intracranial hemorrhage, unspecified
In other words, a high-value code sometimes appears where a nearby, everyday diagnosis was meant. That’s less about clinical judgment and more about the process: pick lists, templates, and the absence of a second look.
What LW Consulting, Inc. Can Do to Help
Being proactive about compliance can help you identify potential risks before they become bigger problems. LW Consulting, Inc. (LWCI) can help review your high-risk list, educate providers on documentation improvement and diagnosis code specificity and status, and identify potential financial risks. We can also review your compliance program to make sure all key areas are covered and provide recommendations to strengthen documentation and improve your internal audit process.
The Bottom Line
Risk adjustment rewards accuracy, not volume. These three audits show what happens when the code on the claim drifts away from the note in the chart: a 76% unsupported rate across the sample and more than $200 million in estimated overpayments. It is not just stopping at the risk adjustment payment model either; diagnosis coding errors are popping up in other audits, like the UPIC.
The fix isn’t exotic. It’s disciplined documentation, careful code selection, and routine internal review aimed at the conditions regulators already know are problematic. CDI teams are well placed to lead that work. The question is whether your organization finds these gaps before the OIG does.
LW Consulting, Inc. (LWCI) offers a comprehensive range of services to assist your organization in maintaining compliance, identifying trends, providing education and training, or conducting documentation and coding audits. For more information, contact LWCI to connect with one of our experts!
| Sources: |
| News: Three OIG Audits Reveal Gaps in Medicare Advantage Diagnosis Coding. ACDIS. (2026, October 15). https://acdis.org/articles/news-three-oig-audits-reveal-gaps-medicare-advantage-diagnosis-coding |
| Office of Audit Services. (2026a, September). Medicare Advantage Compliance Audit of Specific Diagnosis Codes That HumanaChoice. U.S. Department of Health and Human Services | Office of Inspector General. https://oig.hhs.gov/documents/audit/11894/A-05-24-00010.pdf |
| Office of Audit Services. (2026b, September). Medicare Advantage Compliance Audit of Specific Diagnosis Codes That UnitedHealthcare Benefits of Texas, inc.. U.S. Department of Health and Human Services | Office of Inspector General. https://oig.hhs.gov/documents/audit/11917/A-07-24-01215.pdf |
| Office of Audit Services. (2026c, September). Medicare Advantage Compliance Audit of Specific Diagnosis Codes That UnitedHealthcare of Wisconsin, Inc. U.S. Department of Health and Human Services | Office of Inspector General. https://oig.hhs.gov/documents/audit/11890/A-07-24-01214.pdf |
