Cell Count, Viral Load, and Clinical Outcome in Patients with HIV Infection after Highly Active Antiretroviral Therapy

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The summary below is from the full report titled "Clinical Outcome of Patients with HIV-1 Infection according to Immunologic and Virologic Response after 6 Months of Highly Active Antiretroviral Therapy." It is in the 19 September 2000 issue of Annals of Internal Medicine (volume 133, pages 401-410). The authors are S Grabar, V Le Moing, C Goujard, C Leport, MD Kazatchkine, D Costagliola, and L Weiss.

What is the problem and what is known about it so far?

A combination of powerful anti-HIV drugs known as highly active antiretroviral therapy (HAART) can prevent AIDS-related complications in persons with HIV infection. Two laboratory tests, CD4 cell count and viral load, are used to monitor patients' response to HAART. CD4 count is a measure of immune cells; high CD4 counts are better than low ones. The viral load test directly measures the amount of the virus in a person's blood; the lower the viral load, the better. It is not known which test is better at predicting how well patients will do while receiving this therapy.

Why did the researchers do this particular study?

To better understand the relationship among CD4 count, viral load, and clinical outcomes for persons taking HAART.

Who was studied?

The study included 2236 HIV-infected patients from 68 hospitals in France. To be in the study, patients had to be starting HAART for the first time.

How was the study done?

After patients had been receiving HAART for 6 months, the researchers measured CD4 counts and viral loads, which allowed them to classify patients into four categories: 1) complete responders [both CD4 count and viral load improved], 2) immune responders [CD4 count improved but viral load did not], 3) virologic responders [viral load improved but CD4 count did not], and 4) nonresponders (neither CD4 count nor viral load improved). The researchers then followed patients to see who died or developed an AIDS-related complication.

What did the researchers find?

After an average follow-up of 18 months, 69 patients had died and 123 had experienced a new AIDS-related complication. After accounting for other factors that might be related to poor outcomes, complete responders were the least likely and nonresponders were the most likely to die or have a complication. Patients in whom CD4 count improved but viral load did not (immune responders) fared second best, followed by those in whom viral load improved but CD4 count did not (virologic responders).

What were the limitations of the study?

This study did not include patients who died or were lost to follow-up during the first 6 months, so it may have underestimated the risk for poor outcomes. The researchers considered a viral load improved even if virus levels decreased but were still detectable; some researchers would consider only an undetectable virus level to be a virologic response. The study had limited ability to examine the effect of previous treatment with anti-HIV drugs, which can influence how patients respond to HAART.

What are the implications of the study?

Both CD4 count and viral load are useful in monitoring HIV-infected persons taking HAART, but CD4 count seems to be somewhat more important.