The HIV virus slowly infects cells in the body's immune and central nervous system, ravaging the immune system over time to the point that the body is unable to fight back. The medical and scientific communities organize HIV infection into four distinct phases, of which AIDS is the final stage. Doctors diagnose full-blown AIDS using a variety of different methodologies, although this stage may not appear for months to even years following the initial HIV infection.
Blood Work Diagnosis
Doctors routinely perform blood tests to monitor and determine if a person has entered the final stages of HIV. Blood work usually measures the presence of both HIV antibodies, referred to as a person's viral load, along with their CD4+ count, which indicates the number of helper cells found in the immune system to ward off infections. According to the University of South Carolina School of Medicine, a viral load increase together with a CD4+ cell count below 200 is sufficient to warrant an AIDS diagnosis.
WHO Classification Diagnosis
In response to the need to target the ideal time to begin HIV antiretroviral treatment in countries where medical facilities are not always equipped with the supplies necessary to test for CD4+ and viral loads, the World Health Organization developed a staging system. The WHO defines Clinical Stage IV as the final stage of the disease, or full-blown AIDS, according to international AIDS charity AVERT.
Doctors make this diagnosis following the onset of life-threatening and often fatal opportunistic infections that an otherwise healthy immune system could easily fight off. They include Pneumocystis carinii pneumonia, or PCP, toxoplasmosis of the brain, yeast infections of the intestine and the lungs, certain HIV-related cancers, and other viral infections. HIV wasting syndrome, where a person loses more than 10 percent of his body weight and has chronic diarrhea for more than a month, is also a symptom of Stage IV AIDS according to WHO. In addition, doctors will diagnose a person with Stage IV when they remain bedridden for more than half of each day during a month-long period
Multiple Factor Diagnosis
Similar to the WHO's classification system, the AVERT website states that patients are often diagnosed with the final stages of full-blown AIDS if they have one or more of a specific number of severe opportunistic infections or cancers together with a low CD4+ count. Following this criteria, it is possible for someone to be very sick with HIV but not have an AIDS diagnosis.
Life Expectancy
Once full-blown AIDS develops, the University of South Carolina School of Medicine notes that patients rarely survive longer than two years without medical intervention. Thanks to medical advancements, ABC News reporter Katie Snow writes in her article "Living with AIDS, Some Now Embracing a Surprisingly Long Future," that much has changed since the disease first came into the public eye in the 1980s. People who follow a rigorous regimen of antiretroviral medications are able to live years, and possibly even decades, with a formerly fatal disease.
