Evaluating Total Lymphocyte Count as a Surrogate Marker for Immunological Monitoring in HIV Patients Receiving Antiretroviral Therapy: Evidence from a Libyan Cohort

Abstract

Total lymphocyte count (TLC) is a simple and inexpensive laboratory parameter that may provide supportive information about immune status in people living with HIV, particularly in settings where access to CD4 testing is limited. This study evaluated the relationship between TLC and CD4 count and assessed the diagnostic performance of TLC for identifying immune suppression among HIV-infected patients receiving antiretroviral therapy in Libya. A cross-sectional study was conducted among 150 HIV-infected patients receiving routine HIV care at Tripoli University Hospital, Libya. TLC was obtained from complete blood count analysis, while CD4 count was determined by flow cytometry. Pearson and Spearman correlation analyses were used to assess the relationship between TLC and CD4 count. Diagnostic performance was evaluated using sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), receiver operating characteristic (ROC) analysis, and the Youden Index. Multivariate logistic regression was used to evaluate the association between lymphocyte count and immune suppression after accounting for age and sex. TLC showed a statistically significant moderate positive correlation with CD4 count (Pearson r = 0.52 and Spearman ρ = 0.49; both p < 0.001). For identifying CD4 counts < 200 cells/µL, TLC demonstrated 62% sensitivity, 80% specificity, a PPV of 48%, and an NPV of 88%. At the CD4 < 350 cells/µL threshold, sensitivity was 66%, specificity was 74%, PPV was 71%, and NPV was 69%. ROC analysis showed an area under the curve of 0.87. In multivariate analysis, lymphocyte count remained significantly associated with immune suppression after accounting for age and sex, with adjusted odds ratios of 0.11 (95% CI: 0.04–0.31) for CD4 < 200 cells/µL and 0.20 (95% CI: 0.10–0.40) for CD4 < 350 cells/µL (both p < 0.001).  TLC was moderately correlated with CD4 count and remained independently associated with immune suppression. Although TLC may provide useful supportive information when access to CD4 testing is limited, its diagnostic performance is insufficient to replace direct CD4 measurement. TLC may therefore be more appropriate for preliminary immune assessment or patient triage in resource-limited settings.