Assign ICD10 Diagnosis Codes - Certified Professional Coder CPC

1. A patient is diagnosed with major depressive disorder, recurrent, moderate. Which ICD-10-CM code is assigned?
   Answer: F33.1 ICD-10-CM F33.1 covers major depressive disorder, recurrent, moderate. Code F32.1 covers major depressive disorder, single episode, moderate; F33.0 covers major depressive disorder, recurrent, mild; F32.0 covers major depressive disorder, single episode, mild. Two axes of specificity are required: episode type (single vs. recurrent) and severity (mild, moderate, severe).
2. A patient is seen for a vaccination encounter only — the patient is otherwise healthy with no other conditions addressed. Which ICD-10-CM code is first-listed?
   Answer: Z23 ICD-10-CM Z23 covers encounter for immunization. This is the first-listed diagnosis when the patient's only reason for the visit is to receive a vaccine. Code Z00.00 covers an encounter for general adult examination without abnormal findings; Z11.0 covers encounter for screening for intestinal infectious diseases; Z13.88 covers encounter for screening for disorder due to exposure to contaminants. The procedure code for the vaccine administration is reported separately alongside Z23.
3. A patient is diagnosed with sepsis due to methicillin-resistant Staphylococcus aureus (MRSA). Which ICD-10-CM code is assigned?
   Answer: A41.02 ICD-10-CM A41.02 covers sepsis due to methicillin-resistant Staphylococcus aureus (MRSA). Code A41.01 covers sepsis due to methicillin-susceptible Staphylococcus aureus (MSSA); A41.11 covers sepsis due to other specified Staphylococcus; A49.02 covers MRSA infection, site not specified — this is a site-unspecified infection code, not a sepsis code. Resistance status (MRSA vs. MSSA) determines the specific code selection.
4. A patient is diagnosed with atrial fibrillation, chronic (permanent). Which ICD-10-CM code is assigned?
   Answer: I48.21 ICD-10-CM I48.21 covers permanent atrial fibrillation — defined as chronic AF in which rate control is the treatment goal and rhythm conversion is no longer pursued. Code I48.0 covers paroxysmal atrial fibrillation (episodic, self-terminating); I48.11 covers longstanding persistent AF (continuous for more than 12 months); I48.20 covers chronic atrial fibrillation, unspecified. Permanent AF is clinically and administratively distinct from persistent AF and requires I48.21.
5. A patient is diagnosed with acute appendicitis with perforation. Which ICD-10-CM code is assigned?
   Answer: K35.20 ICD-10-CM K35.20 covers acute appendicitis with perforation and peritonitis, without mention of abscess — the correct code for a straightforward perforated appendicitis without abscess formation. Code K35.2 is the unrevised parent entry, now expanded; K35.21 covers perforated appendicitis with peritonitis and abscess; K37 covers unspecified appendicitis. When perforation is documented without abscess, K35.20 is the specific code required.
6. A patient is diagnosed with bilateral primary osteoarthritis of both knees. Which ICD-10-CM code is assigned?
   Answer: M17.0 ICD-10-CM M17.0 covers bilateral primary osteoarthritis of the knee — a single combination code for both knees simultaneously. Code M17.11 covers primary osteoarthritis of the right knee only; M17.12 covers primary osteoarthritis of the left knee only; M17.9 covers osteoarthritis of the knee, unspecified. When bilateral involvement is documented, the bilateral code (M17.0) is always preferred over reporting two unilateral codes.
7. A patient is seen for a follow-up visit after completing treatment for a urinary tract infection. The infection has resolved and no current infection is present. Which ICD-10-CM code is first-listed?
   Answer: Z09 ICD-10-CM Z09 (encounter for follow-up examination after completed treatment for conditions other than malignant neoplasm) is the correct first-listed code when a patient returns for follow-up after a resolved condition with no current disease present. Code N39.0 is the active UTI code and should not be reported when the infection is resolved; Z87.440 and Z87.39 are personal history codes used when the condition is documented as past history — not as the reason for the current follow-up visit.
8. A patient is diagnosed with HIV disease presenting with Pneumocystis jirovecii pneumonia (PCP). Which ICD-10-CM code sequence is correct?
   Answer: B20, B59 Per ICD-10-CM Official Guidelines, when a patient with HIV disease is admitted for an HIV-related condition, B20 (HIV disease) is sequenced first, followed by the code for the HIV-related condition — in this case B59 (Pneumocystosis). Code Z21 is used for asymptomatic HIV infection status, not for a patient with active HIV disease. B59 specifically covers Pneumocystis jirovecii pneumonia and is more specific than J18.9 (unspecified pneumonia).
9. A patient is diagnosed with a primary malignant neoplasm of the upper outer quadrant of the right female breast. Which ICD-10-CM code is assigned?
   Answer: C50.411 ICD-10-CM C50.411 covers malignant neoplasm of the upper outer quadrant of the right female breast. The breast neoplasm code structure identifies morphology type (1=nipple, 2=central, 4=upper outer, 8=overlapping), laterality (1=right, 2=left), and sex (1=female, 2=male). Accurate site and laterality documentation is required for correct code selection.
10. A patient is diagnosed with deep vein thrombosis (DVT) of the right femoral vein, acute. Which ICD-10-CM code is assigned?
    Answer: I82.411 ICD-10-CM I82.411 covers acute deep vein thrombosis of the right femoral vein. Code I82.401 covers acute DVT of an unspecified deep vein of the right lower extremity; I82.4H1 covers acute DVT of the right peroneal vein; I82.491 covers acute DVT of other specified deep vein of the right lower extremity. Accurate DVT coding requires laterality, the specific vessel, and acuity (acute vs. chronic).
11. A patient is diagnosed with stage 3 chronic kidney disease (CKD) with no hypertension. The provider documents stage 3a specifically. Which ICD-10-CM code is assigned?
    Answer: N18.31 ICD-10-CM was updated to include N18.31 (CKD stage 3a) and N18.32 (CKD stage 3b) to allow greater specificity within stage 3. Code N18.3 is now the unspecified stage 3 code when substage is not documented; N18.30 is not a valid ICD-10-CM code. When the provider documents stage 3a specifically, N18.31 is required over the unspecified N18.3.
12. A patient is diagnosed with community-acquired pneumonia due to Streptococcus pneumoniae. Which ICD-10-CM code is assigned?
    Answer: J13 ICD-10-CM J13 covers pneumonia due to Streptococcus pneumoniae. Code J18.9 covers unspecified pneumonia; J15.20 covers pneumonia due to staphylococcus, unspecified; J18.1 covers lobar pneumonia, unspecified organism. When the causative organism is documented, the organism-specific code takes precedence over unspecified pneumonia codes.
13. A patient is diagnosed with type 2 diabetes mellitus with diabetic chronic kidney disease, stage 3. Which ICD-10-CM code is assigned?
    Answer: E11.22 ICD-10-CM E11.22 covers type 2 diabetes mellitus with diabetic chronic kidney disease, stage 3. An additional code for the CKD stage (N18.3) is also required. Code E11.65 covers type 2 DM with hyperglycemia; E11.40 covers type 2 DM with diabetic neuropathy, unspecified; E11.36 covers type 2 DM with diabetic cataract. When diabetic CKD is documented, E11.22 is the combination code rather than reporting E11.9 and N18.3 separately.
14. A patient has COPD and is admitted for an acute lower respiratory tract infection. Which ICD-10-CM code is assigned for the COPD component?
    Answer: J44.0 ICD-10-CM J44.0 covers chronic obstructive pulmonary disease with acute lower respiratory infection. An additional code is required to identify the infection. Code J44.1 covers COPD with acute exacerbation (not infection); J44.9 covers COPD, unspecified — used when no acute complication is documented; J45.51 covers severe persistent asthma with acute exacerbation, which is an asthma code, not a COPD code. The distinction between acute lower respiratory infection (J44.0) and acute exacerbation (J44.1) is clinically significant.
15. A patient is diagnosed with iron deficiency anemia secondary to chronic blood loss. Which ICD-10-CM code is assigned?
    Answer: D50.0 ICD-10-CM D50.0 covers iron deficiency anemia secondary to blood loss, chronic. Code D50.1 covers sideropenic dysphagia (Plummer-Vinson syndrome) — a distinct condition involving iron deficiency with esophageal webs and dysphagia, not chronic blood loss anemia. D50.8 covers other iron deficiency anemias; D50.9 covers iron deficiency anemia, unspecified. When the etiology is documented as chronic blood loss, D50.0 is the specific code required.
16. A patient is involved in a motor vehicle accident and sustains injuries. The external cause of the injuries should be reported using which ICD-10-CM chapter?
    Answer: Chapter 20 (V01-Y99) ICD-10-CM Chapter 20 (V01-Y99) covers External Causes of Morbidity, including transport accidents (V codes), falls (W codes), assault (X codes), and other external causes. Chapter 19 (S00-T88) covers the injuries themselves; Chapter 18 (R00-R99) covers symptoms and abnormal findings; Chapter 21 (Z00-Z99) covers factors influencing health status. External cause codes from Chapter 20 are reported as additional codes, not as the principal diagnosis.
17. A patient is diagnosed with an acute exacerbation of chronic systolic heart failure. Which ICD-10-CM code is assigned?
    Answer: I50.23 ICD-10-CM I50.23 covers acute-on-chronic systolic (congestive) heart failure — used when a patient with known chronic systolic heart failure presents with an acute decompensation. Code I50.20 covers unspecified systolic heart failure; I50.21 covers acute systolic heart failure (new onset, no prior chronic HF); I50.9 covers unspecified heart failure. The combination of chronic underlying HF with acute exacerbation requires the acute-on-chronic code (I50.23) rather than the unspecified code.
18. A patient is diagnosed with type 1 diabetes mellitus with diabetic peripheral angiopathy without gangrene. Which ICD-10-CM code is assigned?
    Answer: E10.51 ICD-10-CM E10.51 covers type 1 diabetes mellitus with diabetic peripheral angiopathy without gangrene. Code E10.52 covers type 1 DM with diabetic peripheral angiopathy with gangrene; E11.51 covers type 2 DM with diabetic peripheral angiopathy without gangrene — the same vascular complication but for type 2 diabetes; E10.59 covers type 1 DM with other circulatory complications. Diabetes type (1 vs. 2) is the first axis of specificity in the E10/E11 code families.
19. A patient suffers an initial encounter for a closed fracture of the right femoral shaft, unspecified displacement. Which ICD-10-CM code is assigned?
    Answer: S72.309A ICD-10-CM S72.309A covers fracture of the femoral shaft, unspecified, initial encounter for closed fracture. Code S72.301A covers displaced fracture of the right femoral shaft, initial encounter; S72.302A covers displaced fracture of the left femoral shaft; S72.301D covers displaced right femoral shaft fracture, subsequent encounter. When displacement is unspecified, the unspecified displacement code (S72.309A) is used.
20. A patient is diagnosed with cellulitis of the left lower leg. Which ICD-10-CM code is assigned?
    Answer: L03.116 ICD-10-CM L03.116 covers cellulitis of the left lower limb. Code L03.115 covers cellulitis of the right lower limb; L03.119 covers cellulitis of an unspecified lower limb. When laterality is documented, the specific laterality code must be assigned — reporting the unspecified code (L03.119) when the side is documented constitutes incomplete coding.

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