On June 5, 1981, the CDC published a report of five cases of Pneumocystis carinii pneumonia among previously healthy young gay men in Los Angeles. After that publication, many more case reports flowed into the CDC. The condition was named acquired immunodeficiency syndrome (AIDS). The virus causing AIDS was identified in 1983 and was eventually named human immunodeficiency virus (HIV).
Since AIDS describes a clinical syndrome with a specific known cause, the preferred descriptive term for AIDS is now “HIV disease,” although “HIV illness” may also be used. On the other hand, a person who tests positive for HIV but does not meet the CDC case definition of HIV disease (AIDS) is said to have “HIV infection.” The nonspecific term “HIV positive” is sometimes used but shouldn't be, because it is an ambiguous description that might imply either HIV infection or HIV disease (AIDS).
Clinicians need to understand the CDC definitions and use the recommended clinical terminology on every encounter to clearly describe patients' status: either HIV infection only or HIV disease (AIDS). Since the CDC recommends that all HIV-infected patients be treated with antiretroviral drugs, treatment does not by itself distinguish HIV infection from HIV disease.
The CDC defines HIV infection as positive results on two different HIV antibody or antigen/antibody tests, or on nonantibody virologic testing. HIV disease (AIDS) is defined in an HIV-infected patient by either a past or present absolute CD4+ T-lymphocyte count of less than 200 cells/mm3 or a current or prior history of any AIDS-defining condition. HIV disease is a permanent diagnosis; once diagnosed, HIV disease never goes away even if the virus becomes undetectable.
Coding guidelines and practices for HIV disease and HIV infection can be complex and confusing. There are only three relevant ICD-10 codes: B20 (HIV disease/AIDS), Z21 (HIV infection/seropositive without AIDS), and R75 (inconclusive HIV test results). Patients must have definitive, conclusive HIV test results for B20 or Z21 to be used.
Assigning HIV infection (HIV positive only without AIDS) is simple if the diagnosis has been clearly documented. However, if the clinician documents only HIV positive, the coder must ask whether the patient has HIV disease (B20) or HIV infection only (Z21). Once a patient has been diagnosed with HIV disease and code B20 has been assigned, coding guidelines state that code Z21 must never again be assigned for that patient's care.
For Medicare, there are six HIV disease/AIDS diagnosis-related groups (DRGs), shown in Table 2. For DRGs 969 and 970, extensive operating room procedures are defined by ICD-10-PCS. For the other DRGs, the terms “major related conditions” and “other related conditions” are important. CMS identifies about 438 “major related condition” codes and about 534 “other related condition” codes (see Table 3 for examples).
Whenever a patient with HIV disease (AIDS) is admitted for any one of these 972 conditions, an HIV DRG (974-977) will be assigned. Code B20 (HIV disease/AIDS) will be assigned as a secondary comorbid diagnosis. Coding software incorporates these HIV-related conditions and automatically assigns the correct DRG.
As an example, consider a patient who has HIV disease and is admitted for pneumococcal pneumonia (a major related condition). The principal diagnosis would be pneumococcal pneumonia (code J13). HIV disease (B20) would also be assigned as a secondary diagnosis. The appropriate DRG would be 976 (HIV with major related condition without complication or comorbidity [CC] or a major complication or comorbidity [MCC]) rather than one of the pneumonia DRGs (177-179 and 193-195). For most DRGs, code B20 would qualify as a CC, but it is excluded as a CC here because the DRG is related to HIV disease.
If a patient with HIV disease is admitted primarily for a condition that is unrelated to AIDS, the principal diagnosis would be the unrelated condition and HIV disease would be a secondary CC diagnosis. Take, for example, a patient with HIV disease who requires laparoscopic cholecystectomy for acute cholecystitis. The principal diagnosis would be acute cholecystitis (K81.0) with a secondary CC diagnosis of HIV disease (B20), resulting in DRG 418 (laparoscopic cholecystectomy with CC).
In summary, always make a clear distinction between HIV disease (AIDS) and HIV infection only, and follow the CDC case definition criteria for HIV disease (AIDS). Become familiar with the CDC's list of AIDS-defining conditions. Note that any patient with HIV disease (AIDS) admitted primarily for a condition considered HIV-related by CMS will be assigned to an HIV DRG (969-977) and HIV disease (code B20) will be a secondary diagnosis. Once a patient has been diagnosed with HIV disease and the code B20 has been assigned, coding guidelines state that code Z21 (HIV infection only) must never again be assigned for that patient.