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  • In the United States of America, the Human Immunodeficiency Virus (HIV) Laboratory Diagnostic Testing Algorithm (Centers for Disease Control and Prevention [CDC]) is used. This algorithm recommends initial testing with an HIV-1/2 antigen/antibody immunoassay (step 1). A single HIV test result cannot provide a definitive HIV-positive diagnosis. If the initial test is reactive, specimens should be tested with an HIV-1/HIV-2 antibody differentiation assay (step 2). In case of negative or indeterminate results at step 2, HIV-1 nucleic acid amplification test (NAAT) is recommended. Globally, the World Health Organization (WHO)–recommended testing algorithms are widely used. The HIV prevalence of the population—either high (≥5%) HIV prevalence or low (<5%) HIV prevalence—is used to inform national HIV testing algorithms (which may vary from country to country).

  • HIV RNA level (viral load) should be ideally used to monitor response to antiretroviral therapy. In resource-limited settings where access to viral load monitoring is limited, CD4 measurements along with clinical assessments may be used to monitor therapy.

  • Absolute CD4 lymphocyte count is widely used for staging HIV disease. Acquired immunodeficiency syndrome (AIDS) is defined as a CD4 <200 cells/mm3. AIDS represents advanced HIV disease that is associated with opportunistic infections or malignancy in the absence of treatment.

  • Although HIV infection cannot be cured currently, antiretroviral drugs are highly effective in suppressing viral replication and enable people living with HIV to enjoy healthy, long, and productive lives. Additionally, they prevent transmission to others.

  • One of the landmark recent advances with the potential to combat stigma has been the recognition of “U = U” (undetectable = untransmittable). There is now evidence-based confirmation that the risk of HIV transmission from people living with HIV, who are on antiretroviral therapy (ART) and have achieved an undetectable viral load in their blood for at least 6 months, is negligible.

General Considerations

As we approach the conclusion of the fourth decade of the HIV/AIDS epidemic, major shifts in the epidemiology and prognosis of HIV disease have occurred. Significant advances in treatment of HIV infection have transformed this fatal disease into a chronic multisystem disease characterized by multiple comorbidities, with noninfectious complications. A major achievement in the past decade has been the scale-up of access to ART globally. In 2017, 21.7 million people living with HIV were receiving ART, with 59% of adults and 52% of children living with HIV receiving lifelong ART. The global ART coverage for pregnant and breastfeeding women living with HIV is high, at 80%. Between 2000 and 2017, new HIV infections fell by 36%, and HIV-related deaths fell by 38%, with 11.4 million lives saved due to ART in the same period. In July 2017, the CDC published a comprehensive analysis of the US HIV care continuum showing that, in 2014, of the estimated 1.1 million people living with HIV in the United States, 85% knew they were infected, ...

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