Which of the following characteristics is unique to a Point of Service (POS) plan?

A Point of Service (POS) plan uniquely combines features from both Health Maintenance Organizations (HMO) and Preferred Provider Organizations (PPO). This hybrid structure allows members to have the flexibility of choosing healthcare providers within a network (similar to HMO) and also the option to go outside the network for care (like a PPO), albeit typically at a higher cost.

This combination of features is what distinguishes a POS plan from other types of health insurance plans. Members can benefit from lower costs associated with using in-network providers while also having the alternative to seek services from out-of-network providers, providing a level of flexibility that is not found in a traditional HMO, which usually requires the use of in-network providers only.

The other options, while relevant to health insurance plans, do not specifically characterize a POS plan uniquely. For example, requiring referrals for specialists is a feature of many managed care plans but is not exclusive to POS plans alone. Hence, the ability to blend HMO and PPO attributes is what truly sets the POS plan apart.