## **Core Concept**
The World Health Organization (WHO) 2010 guidelines for antiretroviral therapy (ART) in HIV-infected adults emphasize the importance of initiating treatment based on specific clinical and immunological criteria. The guidelines aimed to simplify and harmonize ART eligibility criteria to improve access to treatment.

## **Why the Correct Answer is Right**
According to the WHO 2010 guidelines, an HIV-infected adult should be started on antiretroviral therapy (ART) when the CD4 cell count falls below 350 cells/mm³. This recommendation was made to prevent the progression of HIV disease to AIDS, reduce the risk of opportunistic infections, and decrease the likelihood of HIV transmission. The initiation of ART at this threshold helps in preserving the immune system and improving the patient's quality of life and survival.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Initiating ART when the CD4 count is below 200 cells/mm³ is considered late according to the 2010 guidelines, as it aligns more with the definition of AIDS rather than the threshold for starting ART.
- **Option B:** A CD4 count below 500 cells/mm³ was considered for ART initiation in some contexts but was not the specific threshold recommended by the WHO in 2010 for all adults.
- **Option C:** There is no standard recommendation for starting ART based solely on symptoms without considering the CD4 count or clinical staging in the 2010 guidelines.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the WHO guidelines have evolved, and more recent guidelines recommend starting ART regardless of CD4 count or clinical symptoms (Option D: "Regardless of CD4 count or clinical symptoms"). This approach aims to further reduce HIV transmission and improve health outcomes by treating all individuals with HIV infection.

## **Correct Answer:** D. Regardless of CD4 count or clinical symptoms.