REFERENCE RANGES AND SOURCES OF VARIABILITY OF CD4 COUNTS IN HIV-SERONEGATIVE WOMEN AND MEN

Background: CD4 lymphocyte counts are used to monitor immune status in HIV disease. An understanding of the variability of CD4 counts which occurs in the absence of HIV infection is essential to their interpret ation. The sources and degree of such variability have not been extens ively studied. Objectives: To establish reference ranges for CD4 count s in HIV-seronegative women and heterosexual men attending a genitouri nary medicine (GUM) clinic, and to identify possible differences accor ding to gender and cigarette smoking and, in women, any effect of the menstrual cycle, oral contraceptive use and cigarette smoking. Design: Female and heterosexual male patients attending a GUM clinic and requ esting an HIV-antibody test were recruited prospectively. Results from an earlier study of CD4 counts in homosexual men were available for c omparison. Methods: Lymphocyte subpopulation analysis on whole blood b y flow cytometry. Results: The absolute CD4 count and percentage of CD 4 cells (CD4%) were significantly higher in women (n = 195) than heter osexual men (n = 91) [difference between the means lll x 106/l (95% CI 41, 180) and 3.1% (1.30, 4.88)]. The absolute CD4 count and CD4% were also significantly higher in smokers (n = 143) than non-smokers (n = 140) [difference 143 (79, 207) and 2.1% (0.43, 3.81)]. Reference range s for absolute CD4 counts (geometric mean +/- 2SD) were calculated on log transformed data as follows; female smokers 490-1610, female nonsm okers 430-1350, heterosexual male smokers 380-1600, heterosexual male non-smokers 330-1280. Among other variables examined, combined oral co ntraceptive pill use was associated with a trend towards a lower absol ute CD4 count. Changes were seen in CD4% with the menstrual cycle. CD4 counts and CD4% did not differ significantly between heterosexual men and homosexual men (n = 45). Conclusion: There is a significant gende r and smoking effect on CD4 counts. The effects of oral contraceptive use and the menstrual cycle warrant further investigation.