Government Watchdog Agency Finds that Every High-Risk Acute Stroke Diagnosis Submitted by Medicare Advantage Insurers in Audit Was Upcoded

Key Takeaways

• OIG found $462 million overpayment to Medicare Advantage in 2021
• All 97 audited acute stroke diagnoses were unsupported by medical records
• Acute stroke codes boost risk‑adjusted payments more than historical stroke codes
• Report urges CMS to add safeguards for stroke coding accuracy
• Audit adds to evidence of systematic upcoding across Medicare Advantage

Pulse Analysis

Risk‑adjustment is the financial engine behind Medicare Advantage, where insurers receive a per‑member payment adjusted for each enrollee’s health status. Diagnoses submitted by plans feed a risk‑score algorithm; higher scores translate into larger capitated payments. Because the system rewards sicker profiles, insurers have strong incentives to code conditions that carry higher weight, a practice known as upcoding. Acute‑stroke diagnoses are among the most lucrative codes, dramatically increasing a beneficiary’s risk score compared with a mere history of stroke.

The Office of Inspector General’s recent audit uncovered a stark example of this behavior. Reviewing 97 Medicare Advantage members, the OIG determined that every acute‑stroke diagnosis submitted for risk adjustment lacked supporting documentation in the patients’ medical records. The agency estimates that such unsupported coding cost the government roughly $462 million in 2021 alone. While the sample size is modest, the 100% error rate suggests a broader pattern of systematic over‑billing across the private Medicare Advantage market, echoing prior investigations that have identified billions in excess payments.

Policymakers now face pressure to tighten oversight and redesign the risk‑adjustment framework. The OIG’s report urges the Centers for Medicare & Medicaid Services to introduce stricter validation safeguards for acute‑stroke coding, but experts argue that deeper reforms may be needed to eliminate the profit motive that fuels upcoding. Strengthening audit mechanisms, enhancing data transparency, and revisiting the weighting of high‑value diagnoses could reduce wasteful spending and restore confidence in the Medicare Advantage program. Such reforms would protect taxpayers, improve fairness among insurers, and ultimately support better health‑care outcomes for beneficiaries.