Coding “Possible” Diagnoses: Inpatient vs Outpatient Rules Explained

Terms such as possible, probable, suspected, and likely frequently appear in patient records and are a top source of coding errors. Understanding when these diagnoses may be coded and when a query is required is critical for both inpatient and outpatient facility coding.

Inpatient Coding Rules for Possible, Probable, and Suspected Diagnoses

For inpatient admissions:

• A diagnosis documented as possible, probable, suspected, or likely may be coded only if it remains documented as such at the time of discharge.
• “At the time of discharge” refers to the provider’s final assessment, typically reflected in the discharge summary (DS) or final discharge note.
• If the DS does not mention the possible diagnosis, even if a final progress note lists it, it cannot be coded.
• Coders may query if documentation is ambiguous between progress notes and DS.

Key principle: The discharge summary represents the provider’s final assessment and controls coding.

Outpatient and Observation Coding Rules for Uncertain Diagnoses

For outpatient or observation encounters:

• Uncertain diagnoses may never be coded.
• Only confirmed diagnoses documented by the provider during the encounter can be assigned an ICD-10-CM code.
• Documentation of “possible,” “suspected,” or “probable” diagnoses should instead be coded as signs, symptoms, or abnormal findings (e.g., cough, fever, abdominal pain).
  

Bottom line: OP coding is stricter than IP and possible or suspected diagnoses are never coded, even if persistent at the end of the encounter.

When Coders Should Initiate a Query

A query should be initiated when:

• Early documentation lists a possible diagnosis
• Later documentation is conflicting or unclear
• The discharge summary omits the diagnosis entirely

Note: Coders should not assume persistence of a diagnosis across the stay.

Coding Example: Conflicting Documentation at Discharge

IP Example:

• Day 1 Progress Note (IP): "Possible pneumonia: chest X-ray pending.”
• Final Progress Note (IP): “Pneumonia still possible, patient improving.”
• Discharge Summary (IP): “Patient tolerated diet and activity. No acute issues documented.”

Correct Coding (IP):

• Do NOT code pneumonia
  Code the signs/symptoms (e.g., cough, fever)
  Consider a query if clarification is warranted

OP Example:

• Same scenario in an observation or outpatient visit
• Correct Coding (OP): Never code pneumonia; only code presenting symptoms

Key Coding Takeaways for Uncertain Diagnoses

• “At the time of discharge” = provider’s final assessment, typically the DS
• Uncertain diagnoses not referenced at discharge cannot be coded
• Conflicting documentation requires a query, not assumption
• Proper application is a top inpatient audit focus