In which scenario is Medicare considered the primary payer?

Medicare is considered the primary payer when patients have no other insurance or when specific criteria are met that dictate Medicare's role in the payment order. In the scenario where Medicare patients have no other insurance, Medicare acts as the sole payer, handling all the medical expenses for covered services. This ensures that the patient is not left with any gaps in coverage for necessary treatments.

The other scenarios involve conditions where other insurance may play a role. For example, when a patient under 65 has private insurance, that private insurance could potentially be the primary payer. Similarly, Medicare patients over 65 with a Group Health Plan (GHP) from a large employer would typically have that GHP as the primary payer, especially if the employer has 20 or more employees, and Medicare would be the secondary payer. In a non-hospital facility, the primary payer status could depend on the presence of other insurance coverage, rather than Medicare automatically being the primary payer.

Thus, in the context of the question about when Medicare is the primary payer, the scenario that confirms Medicare's role is when patients have no additional insurance coverage.