In ICD-9-CM, what do brackets ( [ ] ) signify?

In ICD-9-CM, brackets serve a specific purpose in the context of coding and indicate synonyms, alternative words, or explanatory phrases for the term or code they accompany. This is important for ensuring that code users understand that there are various ways to describe a condition, which can assist in accurate coding and billing. The presence of brackets highlights that the term inside the brackets is not a required part of the diagnosis but offers clarification or additional context that can guide the coder in selecting the most appropriate code.

In contrast, the other options refer to different coding elements: essential modifiers are typically noted with parentheses, while ill-defined terms could be categorized differently, and directions for alternative codes might be indicated using a different set of symbols or text instructions. Understanding the specific use of brackets helps coders accurately interpret coding guidelines and apply them correctly in practice.