Which of the following may trigger an audit by Medicare?

The answer is focused on "unusual billing patterns compared to peers" because Medicare closely monitors billing practices to detect potential fraud and abuse. When a provider's billing patterns diverge significantly from those of their peers, it raises red flags. This unusual activity may indicate improper coding, unnecessary procedures, or other violations of Medicare policies, which can warrant an audit in order to verify that claims are appropriate and compliant with regulations.

The other options do not typically trigger audits to the same extent. For instance, a high volume of low-risk procedures could indicate a provider is efficient rather than fraudulent. Similarly, the frequency of preventative care services is generally encouraged by Medicare and does not signify improper practice by itself. Higher patient satisfaction scores are positive metrics and not indicators of potential issues in billing practices. Thus, it is the unusual billing patterns that most urgently catch the attention of auditing bodies.