Purpose of ICD-10-CM
A standardized coding system used in the U.S. to classify diagnoses, symptoms, and procedures.
Supports clinical documentation, billing, epidemiological tracking, and quality improvement.
🧩 Key Concepts
1. Structure of ICD-10-CM Codes
Each code has 3–7 characters.
First character: Always a letter.
Characters 2–3: Numeric, define the category.
Characters 4–7: Alphanumeric, provide clinical detail (e.g., severity, location, laterality).
Example:
M54.5 – Low back pain
E11.9 – Type 2 diabetes mellitus without complications
S52.521A – Displaced fracture of left radius, initial encounter
2. Categories of Codes
A00–B99: Infectious diseases
C00–D49: Neoplasms
E00–E89: Endocrine, nutritional, and metabolic diseases
F01–F99: Mental and behavioral disorders
I00–I99: Circulatory system
J00–J99: Respiratory system
K00–K95: Digestive system
M00–M99: Musculoskeletal system
Z00–Z99: Factors influencing health status (e.g., routine exams, social determinants)
3. Laterality
Codes often specify right, left, or bilateral involvement.
Example:
H52.03 – Hypermetropia, bilateral
S93.401A – Sprain of unspecified ligament of right ankle, initial encounter
4. Placeholder “X”
Used when a code requires a 7th character but lacks preceding characters.
Example: T15.91XA – Foreign body in eye, initial encounter
5. 7th Character Extensions
A – Initial encounter
D – Subsequent encounter
S – Sequela (complication or condition resulting from a previous disease)
6. Z Codes
Used for non-disease conditions: screenings, history, social factors.
Examples:
Z00.00 – General adult medical exam
Z63.5 – Disruption of family by separation or divorce
Z59.0 – Homelessness
7. Coding Guidelines
Always code to the highest level of specificity.
Use combination codes when applicable (e.g., diabetes with complications).
Avoid unspecified codes unless documentation is incomplete.
📝 Practice Quiz (15 Questions + Answers)
1. What does ICD-10-CM stand for? Answer: International Classification of Diseases, 10th Revision, Clinical Modification
2. How many characters can an ICD-10-CM code have? Answer: 3 to 7 characters
3. What does the first character of an ICD-10-CM code represent? Answer: A letter indicating the chapter/category
4. What does the code M54.5 represent? Answer: Low back pain
5. Which code category covers mental and behavioral disorders? Answer: F01–F99
6. What does the 7th character “A” indicate? Answer: Initial encounter
7. What is the purpose of the placeholder “X”? Answer: To maintain code structure when a 7th character is required
8. What does Z00.00 represent? Answer: General adult medical examination
9. Which code would be used for homelessness? Answer: Z59.0
10. What does E11.9 represent? Answer: Type 2 diabetes mellitus without complications
11. What is the significance of laterality in ICD-10-CM codes? Answer: It specifies whether the condition affects the right, left, or both sides
12. What does the 7th character “S” indicate? Answer: Sequela (a condition resulting from a previous illness)
13. Which chapter includes codes for the respiratory system? Answer: J00–J99
14. What is the best practice when selecting an ICD-10-CM code? Answer: Code to the highest level of specificity
15. What type of conditions are Z codes used for? Answer: Non-disease conditions like screenings, social factors, and history