Correlation between Venereal Diseases Research Laboratory titers and CD4 T-lymphocyte count determined by flow cytometry in HIV-infected adults: A 5-year study

INTRODUCTION: Venereal Diseases Research Laboratory (VDRL) is one of the key tests for the diagnosis of syphilis; however in HIV-positive individuals, it has been reported to give inappropriate results at times. Thus, this study was conducted to determine if the VDRL test titers vary with the severity of immunosuppression as determined by CD4 cell count. MATERIALS AND METHODS: A total of 2630 samples from HIV-positive adults were tested by qualitative and quantitative VDRL test and if reactive, by Treponema pallidum hemagglutination (TPHA) test. CD4 cell counts were determined at the same time by flow cytometry (BD FACSCount™ system). Correlation between CD4 T-lymphocyte cell count and VDRL titers was sought for. RESULTS: Nearly 6.7% (176/2631) of individuals were VDRL reactive, males more than females (7.6% vs. 5.1%, P = 0.014). Four of the VDRL-reactive patients were found negative by TPHA test and were excluded from further study. VDRL titers ranged from weakly reactive to being reactive at 1:128 (median = 1:2). The CD4 cell count ranged from 23 cells/μl to 883 cells/μl (median = 276 cells/μl, mean = 323.9 ± 200.9). Pearson's coefficient of correlation (R) between CD4 cell count and VDRL titers was calculated to be 0.0559; coefficient of determination (R(2)) was 0.0031. CONCLUSIONS: Although the correlation coefficient shows a positive correlation, the association was very weak. Therefore, CD4 cell count cannot be expected to influence VDRL titers in HIV-positive adults significantly.