Distinguishing AIDS from simply HIV-positive status requires clear, precise diagnosis and is absolutely necessary for coding, DRG assignment and severity-of-illness classification.
The CDC defines AIDS as present in an HIV-positive patient who has or has had any of the following:
- Current or prior diagnosis of an AIDS-defining condition,
- Current or prior CD4+ T-lymphocyte count <200 cells/µL, or
- Current or prior CD4+ T-lymphocyte count <14% of total lymphocytes
An AIDS-defining condition takes precedence over CD4+ counts in making the diagnosis. Such conditions are numerous and include bacterial infections; candidiasis of bronchi, trachi, lungs or esophagus; invasive cervical cancer; and recurrent pneumonia. To see the CDC's full list of conditions, see the Table or go online.
Treatment with antiretroviral drugs does not necessarily mean a patient has progressed from HIV-positive status to full-blown AIDS, since the CDC recommends that all HIV-positive patients be treated with antiretrovirals.
Documenting the distinction
Coding rules require the following in distinguishing HIV-positive status from AIDS.
- ICD-9 code V08, HIV-positive status only without AIDS, is used when a patient has never been diagnosed with AIDS and has never had an AIDS-defining condition. It is only assigned for confirmed HIV and never for suspected, probable or possible cases.
- ICD-9 code 042, AIDS, is assigned if a patient is currently diagnosed with AIDS or was diagnosed at any time in the past (consistent with CDC definitions). Once assigned, code 042 must always be used on every subsequent encounter (inpatient and outpatient).
For coding purposes, AIDS includes the following terms: “AIDS,” “HIV disease,” “ARC” (AIDS-related complex), or “HIV (plus specific documentation of a current or prior AIDS-defining condition)”. Documentation of only “HIV positive,” “HIV illness,” or simply “HIV” will not be coded as AIDS.
The implications for physician documentation are clear. Every admission or outpatient encounter that mentions “HIV” or “HIV positive” must be clarified to state whether the patient has ever been or is currently diagnosed with AIDS.
While the CDC classifies HIV into 4 stages that have clinical utility, the ICD-9 and ICD-10 provide no codes for stage assignment. The CDC's stage 3 definition of HIV is AIDS and should be assigned code 042; simply using the diagnostic term “AIDS” will assist coders.
DRGs: Both simple and complex
Medicare MS-DRG assignment of patients with AIDS is both simple and complex. It's simple because the coding rules are clear and intuitive. It's complex because a very large number of specific diagnoses are classified by coding guidelines as “AIDS-related” conditions (not to be confused with the CDC's AIDS-defining conditions), and these determine which DRG is assigned.
Six MS-DRGs are provided specifically for admissions related to AIDS. When a patient with AIDS is admitted for any of the “AIDS-related” conditions (for example, pneumonia of any cause), an AIDS DRG will be assigned. When a patient with AIDS is admitted for a condition other than an AIDS-related condition (for example, acute exacerbation of COPD), the principal diagnosis is the unrelated condition, and the DRG for that condition will be assigned with AIDS (code 042) as a major complicating comorbidity.
Physicians do not need to know which conditions are classified as AIDS-related; coders will take care of that. However, the importance of clear and consistent documentation of the reason or reasons for admission and any clinical relationship with AIDS cannot be overemphasized.