ICD-10 Guide

Acquired Immunodeficiency Syndrome

ICD-10 Coding for Acquired Immunodeficiency Syndrome(B20, Z21)

PRIMARY SPECIALTYInfectious Disease

COMPLEXITYHigh

LAST UPDATED09/15/2025

Sam Tuffun, PT, DPT

Physical Therapist | Medical Coding & Billing Contributor

Diagnosis Overview

What is Acquired Immunodeficiency Syndrome?

Acquired Immunodeficiency Syndrome (AIDS) is a chronic, life-threatening condition caused by the Human Immunodeficiency Virus (HIV), which progressively weakens the immune system. Key clinical points include: 1) AIDS is characterized by a CD4 cell count of less than 200 cells/mm³ or the presence of opportunistic infections. 2) The disease is transmitted through blood, sexual contact, and from mother to child during childbirth or breastfeeding. 3) Clinical presentation may include recurrent infections, weight loss, fatigue, and neurological complications. 4) Early diagnosis and antiretroviral therapy can significantly improve outcomes and prolong life. 5) Regular monitoring of viral load and CD4 counts is essential for managing the disease. Typical use cases for the B20 and Z21 codes include patients diagnosed with HIV who have progressed to AIDS or are asymptomatic but HIV positive, respectively. The pathophysiology involves the virus attacking CD4 T cells, leading to immune system failure and increased susceptibility to infections and certain cancers.

Key Clinical Considerations:

Diagnosis of AIDS requires a confirmed HIV infection with a CD4 count below 200 cells/mm³ or the presence of specific opportunistic infections.
Signs and symptoms may include persistent fever, night sweats, chronic fatigue, and recurrent infections.
Resolution criteria involve the restoration of CD4 counts above 200 cells/mm³ with effective antiretroviral therapy.
Laboratory findings supporting diagnosis include positive HIV tests (ELISA, Western blot) and low CD4 counts.

Clinical Information

Clinical Criteria & Documentation Requirements

Documentation must include confirmed HIV diagnosis, CD4 counts, and any opportunistic infections.
Compliant documentation examples: 'Patient diagnosed with AIDS based on CD4 count of 180 cells/mm³ and history of pneumonia.' Non-compliant: 'Patient has HIV.'
Documentation template phrases include: 'Patient presents with recurrent infections consistent with AIDS.'
Medical necessity documentation requires evidence of ongoing treatment and monitoring of HIV/AIDS.

Coding Guidelines

Usage Guidelines & Examples

Use B20 for patients with AIDS-related conditions; use Z21 for asymptomatic HIV-positive patients. Example: A patient with a CD4 count of 150 should be coded B20.
Do NOT use B20 for patients who are HIV positive but asymptomatic (use Z21 instead).
Correct usage: B20 for AIDS; incorrect: Z21 for symptomatic AIDS.
Common errors include misclassifying asymptomatic patients as having AIDS; ensure accurate CD4 count documentation.

Code Exclusions

Important Exclusions

Excludes conditions like HIV-related nephropathy (N17.9) and HIV-related cardiomyopathy (I42.9) due to their specific coding.
Alternative codes for excluded conditions should be used based on clinical findings.
Common exclusion errors include misclassifying opportunistic infections as primary diagnoses; ensure accurate coding.
Certain conditions are excluded to maintain specificity in coding for AIDS-related complications.

Specialty Focus

Primary Specialty

Infectious Disease

Specialty Applications

This diagnosis applies to individuals diagnosed with HIV who have progressed to AIDS.
Appropriate in clinical scenarios involving opportunistic infections or severe immunosuppression.
Applicable in both inpatient and outpatient settings, including emergency departments.
Specialty-specific considerations include infectious disease and primary care documentation requirements.

Coding Complexity

High Complexity

This diagnosis requires careful attention to:

Comprehensive clinical documentation
Accurate code selection based on clinical criteria
Proper exclusion considerations
Specialty-specific coding guidelines

Documentation

Documentation Templates

Template 1

Template: 'AIDS diagnosed based on CD4 count of [value] and history of [opportunistic infection].'

Template 2

Template: 'Patient presents with [symptoms] consistent with AIDS diagnosis.'

Template 3

Template: 'Diagnostic criteria met: CD4 count of [value] and [specific findings].'

Template 4

Template: 'Treatment plan includes [interventions] for AIDS management.'

Billing Information

Billing Considerations

Ensure proper documentation for billing
Verify code specificity requirements
Check for any additional codes needed
Review payer-specific guidelines

Common Issues

Insufficient clinical documentation
Incorrect code selection
Missing supporting diagnoses
Timing and frequency documentation

Frequently Asked Questions

What documentation is required for this code?

Detailed documentation must include HIV status, CD4 counts, and any opportunistic infections.

When should this code be used vs similar codes?

Use B20 for AIDS and Z21 for asymptomatic HIV; differentiate based on clinical presentation.

What are common billing issues with this code?

Reimbursement may be denied if documentation does not support the diagnosis; ensure thorough records.

What procedures are commonly associated?

Related CPT codes include 86701 for HIV testing and 80061 for lipid panels in HIV patients.

What is Acquired Immunodeficiency Syndrome?

Key Clinical Considerations:

Diagnosis of AIDS requires a confirmed HIV infection with a CD4 count below 200 cells/mm³ or the presence of specific opportunistic infections.
Signs and symptoms may include persistent fever, night sweats, chronic fatigue, and recurrent infections.
Resolution criteria involve the restoration of CD4 counts above 200 cells/mm³ with effective antiretroviral therapy.
Laboratory findings supporting diagnosis include positive HIV tests (ELISA, Western blot) and low CD4 counts.

Acquired Immunodeficiency Syndrome

Diagnosis Overview

Key Clinical Considerations:

Clinical Information

Clinical Criteria & Documentation Requirements

Coding Guidelines

Usage Guidelines & Examples

Code Exclusions

Important Exclusions

Related ICD-10 Codes

Related CPT Codes

Specialty Focus

Primary Specialty

Specialty Applications

Coding Complexity

Documentation

Documentation Templates

Template 1

Template 2

Template 3

Template 4

Billing Information

Billing Considerations

Common Issues

Frequently Asked Questions

What documentation is required for this code?

When should this code be used vs similar codes?

What are common billing issues with this code?

What procedures are commonly associated?

Acquired Immunodeficiency Syndrome

Diagnosis Overview

Key Clinical Considerations:

Clinical Information

Clinical Criteria & Documentation Requirements

Coding Guidelines

Usage Guidelines & Examples

Code Exclusions

Important Exclusions

Related ICD-10 Codes

Related CPT Codes

Specialty Focus

Primary Specialty

Specialty Applications

Coding Complexity

Documentation

Documentation Templates

Template 1

Template 2

Template 3

Template 4

Billing Information

Billing Considerations

Common Issues

Frequently Asked Questions

What documentation is required for this code?

When should this code be used vs similar codes?

What are common billing issues with this code?

What procedures are commonly associated?