How are ICD-10-CM codes structured and what determines their level of specificity?

• A. They are numeric up to 5 digits; specificity increases with more digits.
• B. They are alphanumeric up to 7 characters; specificity is determined by number of characters and extension digits.
• C. They are fixed 6 characters; specificity is fixed.
• D. They are alphanumeric up to 10 characters; extension digits do not affect specificity.

Answer: (B)

ICD-10-CM codes are alphanumeric and can be up to seven characters long. The first three characters define the general medical condition category, and there is a decimal after the third character. The characters that follow (the extension characters) add detail and specificity. Each additional character refines the code to indicate aspects like the exact condition, the site or laterality, the encounter type (initial/subsequent), and severity or complications. Because more characters provide more detail, a code with the full seven characters is usually the most specific and helpful for accurate billing and reporting. In short, structure is alphanumeric up to seven characters, and specificity grows with the number and meaning of those extended characters.