Final answer:
A significant increase in high reimbursement diagnoses or procedures that do not match the clinical evidence might trigger a CMS audit due to potential upcoding or fraud concerns.
Step-by-step explanation:
A trend in the case mix that might trigger a CMS audit is a significant shift in the acuity or complexity of patients being reported which is not supported by the underlying clinical conditions of the patients. This is often evidenced by a higher than usual number of high reimbursement diagnoses or procedures being claimed. Centers for Medicare and Medicaid Services (CMS) could suspect upcoding or mismatch between reported services and patient conditions, leading to an audit.
An example could be if a healthcare provider is consistently reporting a higher number of patients with complex conditions compared to its benchmarks or peers without corresponding evidence in patient charts. Such discrepancies would raise concerns about potential fraudulent practices or errors in coding. By closely monitoring billing patterns and ensuring accurate documentation, providers can help prevent CMS audits.