Evaluating Total Lymphocyte Count as a Surrogate Marker for CD4 Cell Count in the Management of HIV-Infected Patients in Resource-Limited Settings: A Study from China

Objective: To evaluate the correlation of total lymphocyte count (TLC) and CD4 cell count and the suitability of TLC as a surrogate marker for CD4 cell count of HIV-infected patients in China. Methods: Usefulness of TLC as a surrogate marker for a CD4 cell count <350 cells/mm(3) for HIV-positive patients in China was evaluated by 977 pairs of TLC and CD4 cell count from 977 outpatients. The result was then validated by a literature review which was conducted on 9 relevant articles. Further investigation using the 977 pairs of TLC and CD4 cell count data was done to determine a TLC threshold for predicting a CD4 cell count <500 cells/mm(3). Correlation and receiver operating characteristic (ROC) analysis were performed for both CD4 cell counts, and the sensitivity and specificity were computed. Results: Good correlation was noted between TLC and CD4 count (r = 0.60, 95% CI, 0.56-0.64). TLC obtained a relatively high diagnostic performance (area under ROC curve, 0.80) for predicting a CD4 cell count <350 cells/mm(3), with a sensitivity of 0.65 (95% CI, 0.61-0.68) and a specificity of 0.80 (95% CI, 0.75-0.85) at the TLC threshold of 1570 cells/mm(3). The literature review suggested that for a CD4 cell count <350 cells/mm(3), the optimal TLC threshold was 1500 cells/mm(3), which was similar to the figure presented in this observational study. As for predicting a CD4 cell count <500 cells/mm(3), TLC obtained a high diagnostic performance (area under ROC curve, 0.82) as well with a sensitivity of 0.70 (95% CI, 0.67-0.73) and a specificity of 0.80 (95% CI, 0.73-0.87). Conclusions: When considering the antiretroviral therapy for HIV-infected Chinese individuals, total lymphocyte count can be considered as an inexpensive and easily available surrogate marker for predicting two clinically important thresholds of CD4 count of 350 cells/mm(3) and 500 cells/mm(3).