Adult HIV-infected subjects were recruited from the Jules Stein Eye Institute and the Center for Clinical AIDS Research and Education (CARE) Clinic, UCLA Medical Center, and from Community Eye Medical, a private ophthalmology practice in Pasadena, California, without regard to specific age, gender, race and ethnicity, or the presence or absence of clinically apparent HIV-related ocular disease. Adult HIV-negative control subjects were recruited from the Jules Stein Eye Institute and from the Department of Physiology and Biophysics, USC Keck School of Medicine (Los Angeles, CA), without regard to specific age, gender, or race and ethnicity. Studies on HIV-infected subjects and HIV-negative control subjects were conducted concurrently. All subjects were recruited from June 2002 through March 2003. Excluded were individuals with diabetes mellitus, hypertension, any form of vasculitis, rheumatologic disease, tobacco use, or blood transfusion within the past 3 months. None of the HIV-infected subjects in this study were participants in our previous studies of hemorheologic abnormalities. The study adhered to the tenets of the Declaration of Helsinki and was approved by the UCLA and USC Institutional Review Boards. All participants provided written informed consent.
The following clinical and laboratory data were obtained from medical records for each HIV-infected subject: use of antiretroviral medications, CD4+ T-lymphocyte count within the 3 months before the study (current CD4+ T-lymphocyte count), and lowest previous (nadir) CD4+ T-lymphocyte count.
Blood specimens (20 mL) were obtained from all subjects by venipuncture with a 19-gauge needle and vacuum tubes containing sodium citrate (10 U/mL) or EDTA (1.5 mg/mL). Erythrocyte mean cell volume (MCV) was measured with an automated analyzer (ABX Micros, Irvine, CA) that was routinely calibrated with standards supplied by the manufacturer. Hematocrit was determined using the microhematocrit method (12,000g, 4 minutes). Fibrinogen concentration was determined on frozen citrated plasma Specialty Laboratories (Santa Monica, CA).