Which modifier describes a patient whose severe systemic disease is a constant threat to life?

The correct choice is B, which corresponds to the P4 modifier. This modifier indicates that a patient has a severe systemic disease that poses a constant threat to life. In the context of medical coding and auditing, modifiers are essential for providing additional information about the patient's status and the complexity of their medical condition.

The P4 modifier is explicitly defined within the ASA (American Society of Anesthesiologists) physical status classification system, which categorizes patients based on their medical conditions before undergoing anesthesia. A P4 classification implies that the patient suffers from a significant systemic disease that might affect the outcome of procedures and interventions.

Understanding the implications of P4 classification is crucial for proper coding, billing, and ensuring appropriate patient management during clinical procedures. This highlights the importance of accurately conveying a patient's medical status to ensure that healthcare providers can make informed decisions about their care.

The other modifiers in the choices represent different levels of severity in the ASA classification system, with P2 indicating mild systemic disease and P5 indicating a patient who is not expected to survive without the surgery. This further clarifies why P4 is the appropriate choice in the context of patients facing life-threatening systemic issues.