Which of the following criteria implies that a patient's capacity to attend hospital must be assessed?

The criterion that a patient's capacity to attend hospital must be assessed is based on the need for the patient to demonstrate an understanding of their situation. Capacity involves the ability to comprehend relevant information, weigh the consequences of decisions, and communicate a choice.

When a patient is faced with the possibility of attending the hospital, it is essential that they not only understand their current medical condition and the need for further treatment but also the implications of their choices. This understanding is crucial because it helps ensure that the patient is making informed decisions about their healthcare. If a patient cannot demonstrate this understanding, they may not have the capacity to consent to treatment or transportation, thereby necessitating an assessment to safeguard their health and well-being.

The other options, while indicative of the patient's health status, do not directly relate to an assessment of the patient's capacity. Severe ongoing illness may indicate the need for treatment but doesn’t inherently assess the patient's understanding. Distress and clear communication might suggest readiness for care but do not confirm comprehension. Significant pain can affect a patient's ability to make decisions, but again does not necessarily indicate their level of understanding about the necessity of attending the hospital.