Which of the following is a requirement for coding an external cause?

In coding for external causes of injury or illness, it is essential that there is supporting documentation available. This is a critical requirement because external cause codes often provide context for the circumstances surrounding an injury or condition, which can impact treatment, insurance claims, and statistical data collection. Without proper documentation, the accuracy and validity of the coded information are compromised, making it difficult for healthcare providers and insurers to understand the factors leading to the situation.

Supporting documentation ensures that there is a clear connection between the incident described by the external cause code and the condition or injury being treated. This reinforces the integrity of the medical record and aligns with coding guidelines that emphasize the need for documentation to justify the use of such codes.

In contrast, the other options do not provide an accurate understanding of external cause coding requirements. For example, while linking to a main diagnosis is often necessary for coding in general, it is not a standalone requirement for external causes. Similarly, external cause codes apply to a wider range of incidents beyond car accidents and are relevant in both outpatient and inpatient settings, contrary to what some options suggest.