PREDICTION OF CD4 COUNT FROM CD4 PERCENTAGE - EXPERIENCE FROM 3 LABORATORIES

Objective: CD4 counts have been used to monitor progression of disease in HIV infection as criteria for initiation of therapy, and to strati fy and follow patients in clinical trials. Recently, the Centers for D isease Control and Prevention (CDC) has made CD4 counts part of the cl assification of HIV disease. Because a CD4 percentage may be the only laboratory information available, this study was initiated to determin e whether the correlation between CD4 percentages and CD4 counts is su fficiently high to enable these measures to be substituted for each ot her. Design, setting and patients: One thousand consecutive CD4 measur ements from the University of Washington (UW) were used to create a mo del that was tested using datasets of 1000 CD4 measurements each from Maryland Medical Laboratories (MML) and Rush-Presbyterian-St Luke's Me dical Center (Rush). The patients were not selected for age, sex, risk group or treatment. All patients from MML and Rush were known to be H IV-positive, while the HIV status of all UW patients was unknown. Resu lts: The model predicted that a patient with a CD4 percentage greater- than-or-equal-to 14% would have a CD4 count greater-than-or-equal-to 2 00 x 10(6)/l (if CD4 percentage of 14% was used, 9% of patients would have a CD4 count greater-than-or-equal-to 200 x 10(6)/l), and a patien t with a CD4 percentage greater-than-or-equal-to 27% would have a CD4 count greater-than-or-equal-to 500 x 10(6)/l (if CD4 percentage of 27% was used, 17% of patients would have a CD4 count greater-than-or-equa l-to 500 x 10(6)/l). Conclusions: These CD4 percentage correlations ma y be useful when a white blood cell and lymphocyte count are not avail able to calculate the CD4 count.