THURSDAY, April 24 (HealthDay News) -- Decisions on switching to a second-line series of drugs for HIV/AIDS patients who are failing the first-line regimen are often made on the basis of sophisticated and expensive lab tests.

But a new study shows that survival is only slightly affected if these decisions are based instead on the appearance of clinical symptoms.

Researchers still need to develop less expensive versions of laboratory tests currently used, but lack of test availability shouldn't affect access to highly effective drugs in poorer nations, said the authors of a study in this week's issue of The Lancet.

"I hope that the findings will reassure health policy makers and clinicians that they should continue to make every effort to widen access to ART and not allow any concerns over lack of laboratory monitoring to inhibit this," said study author Andrew Phillips, a professor of epidemiology at Royal Free and University Medical School in London.

The World Health Organization (WHO) recommends that, in lower-income areas, decisions regarding drug treatment for HIV be based on symptoms and, when available, CD4 cell count, rather than viral load.

With viral load, switches to second-line treatment occur when the viral load exceeds 500 copies per millileter.

CD4 cells are a type of immune system cell. Patients generally switch to the second-line drugs when CD4 counts in the blood drop 50 percent from their highest.

WHO-recommended first-line treatment consists of the antiretroviral drugs Zerit (stavudine), Epivir (lamivudine) and Viramune (nevirapine).

Using a computer simulation model to analyze how antiretroviral therapy influences HIV infection, the researchers compared survival rates, switch of second-line medication regimens and development of resistance for three different strategies: monitoring viral load and CD4 cell count or clinical observation.

Over a period of five years, 83 percent of patients using the viral load monitoring strategy, 82 percent using CD4 cell count monitoring, and 82 percent using clinical monitoring survived.

After a period of 20 years, survival rates were 67 percent, 64 percent and 64 percent, respectively. Viral load monitoring showed a slightly longer survival but was not the most cost-effective avenue (at a cost of around $3,500 per life-year gained).

Other experts were concerned that the results might be construed to mean viral load monitoring and CD4 cell count should be abandoned in the developed world.

"It's a great study, but it has no application to First World countries," said Dr. Michael Horberg, director of HIV/AIDS policy at Kaiser Permanente Health Plan in Santa Clara, Calif. "There is wide availability of these tests, and there should be funds to support such monitoring.

"Having said that, it has to be well-acknowledged that in resource-limited nations, CD4 count and viral load monitoring are expensive and have limited availability, and clinical decisions have to be made on the basis of clinical impressions," Horberg continued. "Health-care infrastructures must be sent to resource-limited nations. However, in the interim, clinicians should at least be reassured that their clinical practices are not doing undue harm.

"Infectivity seems to be increased with increased viral load. Not monitoring viral load could mean that highly infectious patients are passing the virus to new people and, indeed, a virus which is already resistant to drugs."

More information

The World Health Organization has more on antiretroviral therapy for HIV infection.

SOURCES: Andrew N. Phillips, Ph.D., professor, epidemiology, Royal Free and University Medical School, London; Michael Horberg, M.D., director, HIV/AIDS policy, Kaiser Permanente Health Plan, Santa Clara, Calif.; April 26, 2008, The Lancet

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