HIV/AIDS and Opportunistic Infections — Clinical Documentation Guide (2026)

🔍 1. Definition

Human Immunodeficiency Virus (HIV) is a retrovirus that targets and destroys CD4+ T-lymphocytes (helper T-cells), progressively impairing cell-mediated immunity. Left untreated, HIV infection advances to Acquired Immunodeficiency Syndrome (AIDS), the most advanced stage, characterized by a CD4 count below 200 cells/µL or the development of an AIDS-defining illness. According to CDC, approximately 1.2 million Americans are living with HIV, and roughly 13% are unaware of their infection.

For coding purposes under FY2026 ICD-10-CM (CMS), the critical distinction is:

• B20 — HIV disease: Assigns when a patient has ever been diagnosed with AIDS or has an AIDS-defining condition (applies for life — once AIDS, always B20).
• Z21 — Asymptomatic HIV infection status: Assigns when HIV is confirmed but the patient has never had an AIDS-defining condition and is currently asymptomatic.
• R75 — Inconclusive laboratory evidence of HIV: Assigns when laboratory testing is inconclusive (e.g., indeterminate Western blot); never used as a confirmed HIV diagnosis.

🗂️ 2. Alternative Terminology

Clinicians, nurses, and patients may use varying language to refer to HIV/AIDS and related conditions. Coders and CDI specialists must recognize these terms to ensure complete and accurate documentation capture.

🩺 3. Signs & Symptoms

Clinical presentation varies significantly by stage of HIV infection. Early (acute) infection, chronic asymptomatic infection, and AIDS each present distinctly. Coders and CDI specialists should flag documented signs/symptoms that may signal transition from asymptomatic HIV (Z21) to AIDS (B20).

Acute HIV Infection (Seroconversion)

• Fever, night sweats, fatigue (flu-like illness 2–4 weeks after exposure)
• Pharyngitis, lymphadenopathy, rash (maculopapular)
• Myalgia, arthralgia, headache
• Oral ulcers, weight loss

Chronic Asymptomatic Phase (Z21)

• Generally no clinical signs; CD4 count typically >500 cells/µL
• Persistent generalized lymphadenopathy possible
• Mild thrombocytopenia or anemia may be present

AIDS-Defining Illness Triggers (→ B20)

• CD4 <200 cells/µL or CD4 percentage <14%
• Recurrent bacterial pneumonia (≥2 episodes in 12 months)
• Pneumocystis jirovecii pneumonia (PCP)
• Esophageal candidiasis
• CMV retinitis/disease
• Disseminated MAC/MAI
• Cerebral toxoplasmosis
• Cryptococcal meningitis
• HIV wasting syndrome (>10% involuntary weight loss)
• Kaposi sarcoma (any site)
• HIV-related lymphoma (C81–C86)
• Progressive multifocal leukoencephalopathy (PML)
• Invasive cervical cancer
• Pulmonary/extrapulmonary tuberculosis

🧭 4. Differential Diagnosis

Several conditions mimic HIV-related immunosuppression or present similarly to AIDS-defining illnesses. Coders must not assume HIV without explicit provider documentation.

📋 5. Clinical Indicators for Coders/CDI

The following clinical indicators should prompt a coder or CDI specialist to review the record for HIV/AIDS coding accuracy, OI documentation, and sequencing. Reference AHIMA and ACDIS resources for query standards.

🦴 6. Anatomy & Pathophysiology

Target Cells and Viral Life Cycle

HIV is an RNA retrovirus belonging to the genus Lentivirus. It primarily infects cells expressing the CD4 surface receptor, including CD4+ T-lymphocytes, macrophages, and dendritic cells. The virus binds CD4 via its gp120 envelope protein, requiring a coreceptor (CCR5 or CXCR4) for cell entry. After reverse transcription, viral DNA integrates into the host genome as a provirus — a reservoir that persists even with effective ART.

Immunological Cascade

Progressive CD4 cell depletion impairs cell-mediated immunity. Key thresholds per NIH AIDSinfo Clinical Guidelines:

• CD4 >500: Near-normal immune function; Z21 typical
• CD4 200–500: Moderate immunosuppression; risk of bacterial infections, herpes zoster
• CD4 <200: Severe immunosuppression; high risk for PCP, toxoplasmosis, CMV — AIDS threshold (B20)
• CD4 <50: Profound immunosuppression; disseminated MAC, CMV retinitis, cryptococcal meningitis

Opportunistic Infection Pathophysiology

• PCP (B59): Pneumocystis jirovecii reactivation causing diffuse alveolar damage; bilateral ground-glass infiltrates on CT; LDH typically elevated.
• CMV (B25.x): Reactivation of latent cytomegalovirus; retinitis (progressive blindness), colitis, esophagitis, encephalitis.
• Candidiasis (B37.x): Opportunistic fungal infection; esophageal form (B37.81) confirms AIDS-defining illness.
• Cryptococcosis (B45.x): Cryptococcus neoformans inhaled from soil; meningitis (B45.1) is the most common AIDS-defining CNS infection.
• Toxoplasmosis (B58.x): Reactivation of Toxoplasma gondii brain cysts causing ring-enhancing lesions; B58.2 = Toxoplasma encephalitis.
• MAC/MAI (A31.2): Disseminated Mycobacterium avium complex; fever, night sweats, weight loss, diarrhea, hepatosplenomegaly.
• TB (A15–A19): Reactivation TB highly prevalent in HIV; extrapulmonary TB more common with advanced immunosuppression.
• Kaposi sarcoma (C46.x): HHV-8 driven vascular tumor; skin lesions, visceral/pulmonary involvement possible; AIDS-defining cancer.

💊 7. Medication Impact / Treatment

Antiretroviral therapy (ART) is the cornerstone of HIV management and has transformed HIV from a terminal illness to a manageable chronic condition. Per NIH AIDSinfo 2026 ART Guidelines, treatment is recommended for all persons with HIV regardless of CD4 count.

Major ART Drug Classes (Coding Relevance)

• NRTIs (nucleoside/nucleotide reverse transcriptase inhibitors): tenofovir (TDF/TAF), emtricitabine, abacavir, lamivudine
• NNRTIs (non-nucleoside RTIs): efavirenz, rilpivirine, doravirine
• INSTIs (integrase strand transfer inhibitors): dolutegravir, bictegravir, raltegravir, cabotegravir
• PIs (protease inhibitors): darunavir/ritonavir, atazanavir/cobicistat
• Entry/attachment inhibitors: ibalizumab (J1742 HCPCS), fostemsavir, lenacapavir
• CCR5 antagonists: maraviroc
• Capsid inhibitors: lenacapavir (long-acting injectable)

OI Prophylaxis and Treatment

• PCP prophylaxis: TMP-SMX (trimethoprim-sulfamethoxazole); code Z29.81 for PCP prophylaxis
• MAC prophylaxis: Azithromycin (Q0144 HCPCS) when CD4 <50
• Toxoplasmosis prophylaxis: TMP-SMX double-strength
• Fluconazole: Candidal infections; J1400 (IV) or oral
• Ganciclovir/valganciclovir: CMV disease treatment
• Liposomal amphotericin B: Cryptococcal meningitis induction
• Ethambutol + rifampin + azithromycin: Disseminated MAC treatment
• Interferon alfa-2b (J1830): HIV-related Kaposi sarcoma

Medication Documentation Coding Notes

Long-term ART use is coded with Z79.899 (long-term current use of other medication) per FY2026 ICD-10-CM guidelines. Most oral ART agents are covered under Medicare Part D (prescription drug benefit), not Part B HCPCS — coders should note that J3490/J3590 apply to infused/injectable antiretrovirals administered in a clinical setting.

Preview ends here. The full guide continues with FY2026 ICD-10-CM code sets, CPT surgical coding, MS-DRG mapping, reimbursement guidance, CDI query templates, and an audit checklist — all available to CCO Members.

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📘 8. ICD-10-CM Guidelines (FY2026)

The ICD-10-CM Official Guidelines for Coding and Reporting, Section I.C.1.a (CMS FY2026), provide specific and detailed instructions for HIV coding. These rules are mandatory for all settings.

I.C.1.a.1 — Patient with Documented HIV Disease (B20)

• Assign B20 when the patient has a confirmed diagnosis of HIV disease (AIDS), regardless of current clinical presentation or viral load.
• B20 is a permanent, lifetime code once assigned — applies to all future encounters.
• Additional codes should be assigned for all documented OIs and HIV-related conditions.

I.C.1.a.2 — HIV with Opportunistic Infections / Related Conditions

• When a patient with HIV disease is admitted for an OI or HIV-related condition: sequence B20 first, followed by the OI/related condition code.
• Example: Admission for PCP in HIV patient → B20, B59
• Example: HIV patient admitted for esophageal candidiasis → B20, B37.81

I.C.1.a.2(b) — HIV with Unrelated Condition

• When a patient with HIV disease is admitted for a condition unrelated to HIV: sequence the unrelated condition first, then B20.
• Example: HIV patient admitted for hip fracture → S72.001A, B20

I.C.1.a.3 — Asymptomatic HIV (Z21)

• Assign Z21 when HIV is confirmed but the patient has never had an AIDS-defining illness and is clinically asymptomatic.
• Z21 is not used once B20 has been established.
• Z21 should not be the principal diagnosis if admitted for another reason — code the reason for admission first, then Z21.

I.C.1.a.4 — Inconclusive HIV Tests (R75)

• Assign R75 when laboratory evidence of HIV is inconclusive (indeterminate Western blot, indeterminate antibody test).
• Do not use R75 to imply confirmed HIV infection — confirmatory testing is required before assigning B20 or Z21.

I.C.1.a.5 — HIV in Pregnancy

• Assign O98.7x first (HIV complicating pregnancy) when the patient has HIV and is pregnant, regardless of trimester.
• Add B20 or Z21 as additional codes to further specify HIV disease status.
• The obstetric code (O98.7x) always sequences first during the pregnancy episode per Guideline I.C.15.

I.C.1.a.6 — Newborns with HIV Exposure

• Z20.6 — Contact with and (suspected) exposure to HIV; used for newborns exposed perinatally when HIV status is unknown.
• R75 — Inconclusive laboratory evidence of HIV; used when newborn tests are indeterminate.
• Do NOT assign B20 or Z21 to a newborn unless HIV infection is confirmed by a provider.

MS-DRG Implications

Per CMS IPPS MS-DRG grouper, B20 as a principal diagnosis maps to:

• MS-DRG 969–970 — HIV with Extensive OR Procedure: w/ MCC / w/o MCC
• MS-DRG 974–976 — HIV with Major Related Condition: w/ MCC / w/o MCC
• MS-DRG 977 — HIV without other related condition

The presence of documented sepsis (A41.x, HCC 2), respiratory failure, or other MCCs/CCs significantly elevates MS-DRG weight and reimbursement — making accurate OI documentation critical for appropriate payment.

🔢 9. ICD-10-CM Code Set (FY2026)

All codes verified against FY2026 ICD-10-CM Tabular List (CMS) effective October 1, 2025.

🔎 10. Indexing

When locating HIV/AIDS codes in the FY2026 ICD-10-CM Alphabetic Index, use these primary index entry paths:

🏥 11. CPT (2026)

CPT codes verified against the AMA CPT 2026 code set. All HIV-related laboratory testing is typically performed in an outpatient or reference lab setting.

🧾 12. HCPCS (2026)

HCPCS codes relevant to HIV/AIDS management, per CMS HCPCS 2026 release. Note: Most oral antiretroviral agents are covered under Medicare Part D and do not have reportable Part B HCPCS codes — only infused/injectable agents administered in the clinical setting use Part B HCPCS billing.

📚 13. AHA Coding Clinic (Recent Guidance)

The AHA Coding Clinic has issued multiple advisories on HIV/AIDS coding. The following represent key guidance applicable to FY2026:

• HIV Disease Sequencing (I.C.1.a): Coding Clinic has consistently affirmed that B20 sequences first when the admission is related to HIV disease or OI, reinforcing guideline I.C.1.a.2. Providers should document the causal relationship between HIV and OI explicitly.
• B20 vs. Z21 Distinction: AHA Coding Clinic has clarified that once a patient has been documented with AIDS or an AIDS-defining condition, B20 applies for all subsequent encounters — consistent with the “lifetime code” principle. Clinical coders should audit records for historical AIDS documentation before defaulting to Z21.
• HIV Wasting Syndrome: Coding Clinic guidance supports coding B20 + R64 (cachexia) when the provider explicitly documents HIV wasting syndrome; documentation should include weight loss percentage and absence of other explanatory etiology.
• OI Causal Linkage: Coding Clinic emphasizes that opportunistic infections in HIV patients are presumed HIV-related when they are established AIDS-defining conditions. A formal “due to HIV” statement in every note is ideal but the OI list per CDC suffices for coding purposes when the provider documents HIV disease (B20).
• HIV in Pregnancy: Coding Clinic reaffirms O98.7x always sequences first in obstetric encounters; B20 or Z21 added as additional code. The trimester-specific 7th character is required.
• Candidal Sepsis (B37.7): When candidal sepsis is the reason for admission in an HIV patient, guideline direction depends on whether it was caused by HIV immunosuppression — if so, sequence B20 first, then B37.7; if coding sepsis as principal, ensure A41.89 is also considered per sepsis guidelines (I.C.1.d).

💰 14. HCC / Risk Adjustment (v28)

CMS-HCC model version 28 (effective January 1, 2024 for 2026 payment year) applies to Medicare Advantage and Part C risk adjustment per CMS Risk Adjustment documentation. HIV/AIDS generates one of the highest RAF impacts of any single diagnosis.

Risk Adjustment Documentation Best Practices

• HIV disease (B20) must be documented, evaluated, and managed (DEM) at each applicable encounter to capture HCC 1 for that plan year.
• ART prescription or documented HIV medication management at the visit supports the DEM standard.
• CD4 count documented and reviewed at the encounter strengthens the DEM evidence.
• OI documentation (when present) adds additive HCC weight — providers should specifically document the OI diagnosis, not just treatment.
• Kaposi sarcoma (HCC 22) requires specific site coding (C46.0–C46.9); “KS” alone without site specificity should prompt a query.

✍️ 15. CDI Query Templates

All query templates below are ACDIS and AHIMA compliant — non-leading, multiple-choice format, clinically appropriate. Queries are for clarification only and must be based on clinical indicators present in the medical record.

🧑‍⚕️ 16. Treatments (Clinical)

Clinical treatment information is provided for CDI and clinical context; this section supports documentation accuracy and is not a substitute for clinical judgment. Current guidelines are from NIH AIDSinfo Clinical Guidelines (2026) and CDC HIV Clinical Resources.

Antiretroviral Therapy (ART)

Standard of care is a 3-drug regimen (typically 2 NRTIs + 1 INSTI). Preferred initial regimens per NIH 2026 guidelines:

• Bictegravir/tenofovir alafenamide/emtricitabine (BIC/TAF/FTC) — Biktarvy; preferred for most treatment-naive patients
• Dolutegravir/abacavir/lamivudine (DTG/ABC/3TC) — Triumeq; requires HLA-B*5701 testing
• Dolutegravir + tenofovir alafenamide/emtricitabine — preferred in pregnancy (after first trimester)
• Long-acting cabotegravir + rilpivirine (CAB+RPV) — monthly or every-2-month IM injection for virally suppressed patients
• Lenacapavir — twice-yearly subcutaneous injection (capsid inhibitor); approved for multidrug-resistant HIV

OI Treatment Summary

• PCP (B59): TMP-SMX 15–20 mg/kg/day TMP × 21 days; prednisone for moderate-severe (PaO2 <70 mmHg)
• CMV retinitis (B25.8): Ganciclovir IV or oral valganciclovir; ART initiation/optimization essential
• Candidal esophagitis (B37.81): Oral fluconazole 200 mg × 14–21 days; IV for severe cases
• Cryptococcal meningitis (B45.1): Liposomal amphotericin B + flucytosine (induction) → fluconazole (consolidation/maintenance)
• Toxoplasma encephalitis (B58.2): Pyrimethamine + sulfadiazine + leucovorin; lifelong secondary prophylaxis until CD4 >200 on ART
• Disseminated MAC (A31.2): Clarithromycin + ethambutol ± rifabutin; concurrent ART
• Pulmonary TB (A15.x): Rifampin-based RIPE regimen (rifampin, isoniazid, pyrazinamide, ethambutol) × 6 months; complex drug interactions with ART
• Kaposi sarcoma (C46.x): ART optimization (immune reconstitution); liposomal doxorubicin for systemic/visceral KS; interferon alfa for limited cutaneous disease
• AIDS-related lymphoma (C81–C86): Combination chemotherapy (CHOP, R-CHOP) + concurrent ART; CNS lymphoma: methotrexate-based regimens

OI Prophylaxis Thresholds

• PCP prophylaxis: CD4 <200 → TMP-SMX DS daily (Z29.81); discontinue when CD4 sustained >200 on ART
• Toxoplasmosis prophylaxis: CD4 <100 + positive Toxoplasma IgG → TMP-SMX DS daily
• MAC prophylaxis: CD4 <50 → azithromycin weekly (Q0144) or clarithromycin; discontinue when CD4 >100 × 3 months on ART
• Cryptococcal antigen screening: CD4 <100 in high-prevalence settings

🎓 17. Patient Education / Summary

This section provides a clinician-ready summary of patient education points for HIV/AIDS documentation completeness. CDI specialists may use these points to facilitate accurate provider-patient communication documentation.

Key Patient Education Topics for Documentation Completeness

• HIV is a lifelong condition: Once diagnosed with AIDS (B20), the documentation and coding reflect this permanent status regardless of treatment success.
• Importance of ART adherence: Consistent adherence suppresses viral load (goal: undetectable), preserves CD4 count, and prevents OI development. Document adherence status at each visit.
• OI awareness: Patients should report fever, night sweats, unexplained weight loss, vision changes, dysphagia, or neurological symptoms immediately — each may represent an OI requiring urgent evaluation and specific diagnosis coding.
• CD4 monitoring schedule: Regular CD4 counts guide prophylaxis initiation and OI risk stratification; document results and clinical interpretation at each visit.
• Co-infection screening: Annual STI screening (syphilis, gonorrhea, chlamydia), hepatitis B/C co-infection status, TB skin test/IGRA — all generate additional ICD-10 documentation opportunities.
• Wasting/nutrition: Weight monitoring at every visit; involuntary weight loss >10% should prompt documentation of HIV wasting syndrome evaluation.
• Pregnancy and HIV: Women of childbearing age should have HIV status documented; ART during pregnancy prevents mother-to-child transmission; O98.7x coding and perinatal exposure documentation for newborn.
• PrEP for HIV-negative partners: Document HIV-negative status and PrEP indication; Z11.4 (HIV screening encounter) and Z79.899 (long-term PrEP use) for the uninfected partner.

Documentation Summary for Coders

For optimal coding accuracy in HIV/AIDS cases, ensure the medical record contains:

1. Confirmed HIV diagnosis type: AIDS (B20) or asymptomatic (Z21) — explicitly stated by provider
2. CD4 count with clinical interpretation documented at the encounter
3. Viral load result documented and clinically interpreted
4. Current ART regimen documented with adherence status
5. All active OIs named, with site specificity and causal link to HIV stated
6. Wasting syndrome evaluated — weight loss percentage documented if applicable
7. Prophylaxis agents and indications documented
8. Pregnancy status with HIV complication code when applicable
9. Co-infections (TB, hepatitis B/C, syphilis) identified and documented separately
10. Kaposi sarcoma or lymphoma site specificity for HCC accuracy

For additional HIV coding resources, see the FY2026 ICD-10-CM Official Guidelines (CMS), NIH AIDSinfo Clinical Guidelines, CDC HIV Treatment Guidelines, and AHIMA Coding Resources.

About this Guide

This Clinical Documentation Guide is published by CCO Academy and is intended for credentialed coding, CDI, and clinical documentation professionals. Content is updated for FY2026 ICD-10-CM (effective October 1, 2025). All code assignments should be verified against the official ICD-10-CM Tabular List, AHA Coding Clinic, and applicable payer-specific policies. This guide does not constitute legal, medical, or compliance advice.

Last reviewed: April 2026 · Next scheduled review: October 2026 (FY2027 update)