By Sean Henahan, Access Excellence

PITTSBURGH - A new AIDS test provides clinicians with a way to predict how quickly an HIV-positive person will progress to AIDS, report researchers.

The new test, called branched DNA signal amplification, measures the amount of HIV RNA in the plasma of infected patients. The test more accurately predicts HIV disease outcome than other commonly used markers including CD3 cell counts, p24 antigen levels or neopterin and beta2-microglobulin levels, according to a study conducted at the University of Pittsburgh.

"Our findings provide strong evidence that the course of HIV infection is directly related to the levels of HIV RNA that are present very early after infection. All other markers were less predictive than that of HIV RNA levels. Confirming this relationship creates new opportunities for increasing our knowledge of the disease, developing more effective therapies and, most importantly, helping physicians individualize patient management," said John Mellors, M.D., Director, Pitt Treatment Evaluation Unit.

Dr. Mellors and colleagues used the experimental test to evaluate 62 patients newly infected with HIV. Patients were tested at six month intervals for at least two years. Fewer than six percent of patients with relatively low levels of HIV RNA (10,000 Eq/ml or less) developed AIDS during the study period. in contrast, more than 80% of patients with higher levels of HIV RNA developed AIDS during the same period.

The bDNA test was far more predictive of progression than current assays. Levels of CD4 T-cells have long been used as a surrogate marker to measure disease progression and to monitor response to antiviral treatments. However, changes in CD4 counts sometimes do not decline until well after the amount of HIV in the system has increased, he noted.

The course of disease from initial infection with HIV to development of AIDS varies widely among individuals. The median interval between infection and AIDS is ten years, but some patients can progress to AIDS within only a couple of years, while others have gone for more than ten years without signs of immunologic decline. The reasons for this are unknown, and until now no test has been able to predict which patients are likely to progress more rapidly to AIDS.

The new test should make a large difference in the design of clinical trials and in clinical practice. The test could help clinical researchers design studies of patients with similar risks for progression. It would also provide clinicians with an indication of which patients should be treated most urgently.

While the branched DNA assay is not quite as sensitive as PCR-based detection methods, the new test has the advantage of being able to be performed in standard clinical laboratories without the need for special procedures or facilities. The new test is also quite rapid- duplicate samples can be run within 36 hours. These characteristics make the test suitable for everyday clinical practice, he said.

For more details see: Annals of Internal Medicine, 1995; 122;573-579; Mellors et al.