CD4 counts and AIDS survival.

Last fall, preliminary findings hinted that AIDS patients taking the drug zidovudine (AZT) have a better chance of prolonging their survival if their levels of certain immune cells, called CD4, stay above 50 cells per cubic millimeter of blood (SN: 11/4/89, p.298). A retrospective study of 55 people with AIDS or severe AIDS-related complex (ARC) has now confirmed that finding, reports a research group headed by Robert Yarchoan of the National Cancer Institute in Bethesda, Md. Patients "were very unlikely to die from HIV infection as long as their CD4 counts remained at 50 cells/[mm.sup.3] or higher," the team writes in the Aug. 1 ANNALS OF INTERNAL MEDICINE.

Of the 44 patients who died during the four-year study period, 40 had known CD4 levels below the critical limit within the six months prior to death, the researchers say. They emphasize that a CD4 count below 50 should not be viewed as a sign of imminent death; some patients in the study survived more than three years after their counts dropped below the critical level.