Which statement about ICD-10 is true?

• A. They classify professional services provided by a clinician.
• B. They begin with a number.
• C. They are always exactly 4 digits long.
• D. They will contain 3 to 7 characters and the first character will always be a letter.

Answer: (D)

ICD-10 codes are alphanumeric identifiers for diagnoses with a specific structure: the first character is a letter, and the total length ranges from 3 to 7 characters, with a decimal placed after the first three characters to separate the category from the more detailed subcategories. This is why the true statement describes codes that contain 3 to 7 characters and start with a letter. For example, codes like E11.9 or M54.5 illustrate the format.

The other statements don’t fit: professional services coded separately use CPT/HCPCS, not ICD-10; ICD-10 codes do not begin with a number; and they are not fixed at exactly four digits.