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.

Abstract

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. 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. 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). 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).