Progress realized: trends in HIV-1 viral load and CD4 cell count in a tertiary-care center from 1999 through 2011

Abstract

Background: HIV-1 RNA and CD4 cell counts are important parameters for HIV care. The objective of this study was to assess the overall trends in HIV-1 viral load and CD4 cell counts within our clinic.

Methods: Patients with at least one of each test performed by the Infectious Diseases Laboratory from 1999 through 2011 were included in this analysis. By adapting a novel statistical model, log(10) HIV-1 RNA means were estimated by month, and log(10)-transformed HIV-1 RNA means were estimated by calendar year. Geometric means were calculated for CD4 cell counts by month and calendar year. Log(10) HIV-1 RNA and CD4 cell count monthly means were also examined with polynomial regression.

Results: There were 1,814 individuals with approximately 25,000 paired tests over the 13-year observation period. Based on each patient's final value of the year, the percentage of patients with viral loads below the lower limit of quantitation rose from 29% in 1999 to 72% in 2011, while the percentage with CD4 counts <200 cells/µL fell from 31% to 11%. On average annually, the mean HIV-1 RNA decreased by 86 copies/mL and the mean CD4 counts increased by 16 cells/µL. For the monthly means, the correlations (R(2)) from second-order polynomial regressions were 0.944 for log(10) HIV-1 RNA and 0.840 for CD4 cell counts.

Conclusions: Marked improvements in HIV-1 RNA suppression and CD4 cell counts were achieved in a large inner-city population from 1999 through 2011. This success demonstrates that sustained viral control with improved immunologic status can be a realistic goal for most individuals in clinical care.

Figure 1. Distribution of final HIV-1 RNA and CD4 cell counts.

(A) Final HIV-1 RNA and (B) final CD4 cell counts by calendar year for 1,814 unique patients tested for both parameters at least once from 1999 through 2011. The number of individuals each year ranged from 575 in 1999 to 854 in 2011. The HIV-1 RNA lower limit of quantitation was 50 copies/mL from 1-1-99 to 10-17-02, 75 copies/mL from 10-18-02 to 3-4-08 and 40 copies/mL from 3-5-08 to 12-31-11.

Figure 2. Annual and monthly means of HIV-1 RNA and CD4 cell counts.

(A) Annual log₁₀-transformed HIV-1 RNA means and CD4 cell count geometric means calculated from each patient's final values by calendar year. (B) Monthly log₁₀ HIV-1 RNA means and (C) CD4 cell count geometric means calculated from all testing in a given month which represented 21–24% of that year's number of patients (575 persons in 1999 to 854 in 2011). Two-limit Tobit, censored regression models were used to estimate the true mean log₁₀ HIV-1 RNA values by month and year. CD4 cell counts of 0 were assigned the value of 1 cell/µL.