Key Takeaways
- Z codes (Z00-Z99) represent factors influencing health status and contact with health services — they are used for encounters that are not related to illness or injury (e.g., screening, preventive care, history).
- External cause codes (V00-Y99) describe the cause of injury, the place of occurrence, activity, and status — they are never reported as the principal/first-listed diagnosis.
- Neoplasm coding requires the Neoplasm Table and follows a specific hierarchy: primary site, secondary (metastatic) site, benign, uncertain behavior, in situ, unspecified.
- When sequencing ICD-10-CM codes, the reason for the encounter (chief complaint/condition) is listed first, followed by any coexisting conditions that affect management.
- Combination codes capture both a condition and its complication or manifestation in a single code, eliminating the need for multiple codes.
- Code first/use additional code pairings indicate mandatory sequencing: the "code first" condition is the underlying cause listed first, and the "use additional code" is listed second.
- Diabetes coding (E08-E13) requires a combination code that includes the type of diabetes and any associated complications (e.g., E11.65 = Type 2 DM with hyperglycemia).
- Injuries are coded by anatomical site, type, laterality, and encounter type (7th character), with separate codes for the injury and external cause.
ICD-10-CM Coding Practice & Chapter-Specific Guidelines
Beyond the general structure and guidelines, the CPC exam tests your ability to apply chapter-specific guidelines to real-world coding scenarios. This section covers the most heavily tested topics within ICD-10-CM on the CPC exam.
Z Codes (Factors Influencing Health Status)
Z codes (Z00-Z99) are used when the reason for the encounter is not an illness, injury, or active disease. They represent reasons for encounters such as:
| Z Code Category | Examples |
|---|---|
| Screening encounters | Z12.11 (screening for malignant neoplasm of colon) |
| Preventive care | Z23 (encounter for immunization) |
| Personal/family history | Z85.3 (personal history of malignant neoplasm of breast), Z80.0 (family history of malignant neoplasm of digestive organs) |
| Status codes | Z96.641 (presence of right artificial hip joint) |
| Observation and evaluation | Z03.89 (observation for suspected condition ruled out) |
| Aftercare | Z48.812 (encounter for surgical aftercare following surgery on the circulatory system) |
| Counseling | Z71.3 (dietary counseling and surveillance) |
Z Code Sequencing Rules
- Z codes can be first-listed or secondary depending on the circumstances
- Some Z codes are first-listed only (e.g., Z23 for immunization encounters)
- Some Z codes should never be first-listed (e.g., Z77-Z99 history/status codes when the encounter is for an active condition)
- Z codes can be used in any healthcare setting
External Cause Codes (V00-Y99)
External cause codes describe:
- How the injury occurred (cause)
- Where it occurred (place of occurrence)
- What the patient was doing (activity)
- Status (civilian, military, etc.)
Key Rules for External Cause Codes
- Never report as the first-listed/principal diagnosis — always secondary
- Use the full range of external cause codes to describe the circumstances as completely as possible
- Place of occurrence (Y92), activity (Y93), and external cause status (Y99) codes supplement the main external cause code
- External cause codes are required by many payers and are tested on the CPC exam
- The 7th character for external cause codes follows the same A/D/S convention (initial, subsequent, sequela)
Neoplasm Coding
Neoplasm coding uses the Neoplasm Table in the Alphabetic Index:
| Column | Definition | Example |
|---|---|---|
| Malignant Primary | Original site of the cancer | C50.911 (malignant neoplasm of breast, right) |
| Malignant Secondary | Site where cancer has metastasized (spread) | C79.51 (secondary malignant neoplasm of bone) |
| Ca in situ | Abnormal cells present but have not invaded surrounding tissue | D05.90 (carcinoma in situ of breast) |
| Benign | Non-cancerous growth | D24.1 (benign neoplasm of right breast) |
| Uncertain behavior | Pathologist cannot determine if benign or malignant | D48.60 (neoplasm of uncertain behavior of breast) |
| Unspecified | Behavior is not documented | D49.3 (neoplasm of unspecified behavior of breast) |
Sequencing for Neoplasm Coding
- Active treatment directed at the primary neoplasm → Code the primary neoplasm first
- Active treatment directed at the secondary (metastatic) site → Code the secondary neoplasm first, primary second
- Encounter solely for chemotherapy/radiation → Z51.11 (chemo) or Z51.0 (radiation) is first-listed, followed by the neoplasm code
Diabetes Coding (E08-E13)
Diabetes is coded using combination codes that capture the type of diabetes and associated complications:
| Category | Type |
|---|---|
| E08 | Diabetes due to underlying condition |
| E09 | Drug or chemical induced diabetes |
| E10 | Type 1 diabetes mellitus |
| E11 | Type 2 diabetes mellitus |
| E13 | Other specified diabetes mellitus |
Key Diabetes Coding Rules
- Type 2 is the default when the type is not documented
- Use as many codes as needed from a single category to describe all complications
- If the patient uses insulin and has Type 2 DM, add Z79.4 (long-term use of insulin) — do NOT change to Type 1
- Common combinations:
- E11.65 = Type 2 DM with hyperglycemia
- E11.621 = Type 2 DM with foot ulcer (use additional code for ulcer site)
- E11.40 = Type 2 DM with diabetic neuropathy, unspecified
Sequencing Rules Summary
| Scenario | First-Listed Code | Additional Codes |
|---|---|---|
| Acute + chronic condition | Acute condition | Chronic condition |
| Symptom with confirmed diagnosis | Confirmed diagnosis | (Do NOT code the symptom if integral) |
| Two equal conditions | Either may be first-listed | List both |
| Neoplasm + chemo encounter | Z51.11 (chemo) | Neoplasm code |
| Injury encounter | Injury code | External cause code(s) |
| Code first / use additional | "Code first" condition | "Use additional code" condition |
Combination Codes
A combination code is a single code that classifies:
- A diagnosis with a common associated manifestation or complication
- Two diagnoses together
- A diagnosis with an associated complication
Example: K50.011 = Crohn disease of small intestine with rectal bleeding (combines the disease + the complication in one code). You do NOT need a separate code for the rectal bleeding.
Rule: When a combination code fully describes all elements of the condition, use only the combination code. Do NOT assign additional codes for the included components.
A patient with Type 2 diabetes mellitus on daily insulin presents with diabetic peripheral neuropathy. Which code(s) should be reported?
A patient presents for a follow-up colonoscopy screening. No polyps or abnormalities are found. The correct first-listed diagnosis code is:
A patient is admitted for chemotherapy treatment of primary lung cancer with liver metastases. What is the correct sequencing?
Arrange the correct steps for looking up an ICD-10-CM diagnosis code:
Arrange the items in the correct order
Match each ICD-10-CM code category to its diabetes type:
Match each item on the left with the correct item on the right
An external cause code (V00-Y99) should be sequenced as:
When the type of diabetes is not documented, ICD-10-CM defaults to Type ___.
Type your answer below