What is the most appropriate recommendation for a regulatory professional when an error in a software subroutine has caused a serious injury?

The most appropriate recommendation in this situation is to discuss the incident with the authorities and send an advisory letter to each customer. This approach demonstrates accountability and proactive communication regarding the potential risks associated with the software subroutine error.

Informing regulatory authorities ensures that the incident is reported appropriately, complying with legal and ethical obligations. It also helps build transparency in regulatory compliance, as the authorities may need to assess the implications of the error on public health and safety and may guide further action, if necessary.

Sending an advisory letter to customers is also crucial because it allows for direct communication about the risks they may face due to the error. This notification is essential for enabling customers to make informed decisions regarding the use of the medical devices affected by the issue. It fosters trust and supports customer safety, showing that the company takes the incident seriously and is willing to address the implications promptly.

In the context provided, options like product recall or corrective action might be considered later as part of a broader response, but immediate communication with relevant stakeholders is critical in addressing the serious nature of the injury caused by the error.