Objective: To inform guidelines concerning when to initiate combination antiretroviral therapy (ART), we investigated whether CD4+ T-cell counts (CD4 cell counts) continue to increase over long periods of time on ART. Losses-to-follow-up and some patients discontinuing ART at higher CD4 cell counts hamper such evaluation, but novel statistical methods can help address these issues. We estimated the long-term CD4 cell count trajectory accounting for losses-to-follow-up and treatment discontinuations.
Design: The study population included 898 US patients first initiating ART in a randomized trial (AIDS Clinical Trials Group 384); 575 were subsequently prospectively followed in an observational study (AIDS Clinical Trials Group Longitudinal Linked Randomized Trials).
Methods: Inverse probability of censoring weighting statistical methods were used to estimate the CD4 cell count trajectory accounting for losses-to-follow-up and ART discontinuations, overall and for pretreatment CD4 cell count categories (≤200, 201–350, 351–500, and >500 cells/μl).
Results: Median CD4 cell count increased from 270 cells/μl pre-ART to an estimated 556 cells/μl at 3 and 532 cells/μl at 7 years after starting ART in analyses ignoring treatment discontinuations, and to 570 and 640 cells/μl, respectively, had all patients continued ART. However, even had ART been continued, an estimated 25, 9, 3, and 2% of patients with pretreatment CD4 cell counts of 200 or less, 201–350, 351–500, and more than 500 cells/μl would have had CD4 cell counts of 350 cells/μl or less after 7 years.
Conclusion: If patients remain on ART, CD4 cell counts increase in most patients for at least 7 years. However, the substantial percentage of patients starting therapy at low CD4 cell counts who still had low CD4 cell counts after 7 years provides support for ART initiation at higher CD4 cell counts.
aCenter for Biostatistics in AIDS Research, Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA
bUniversity of California, San Diego, California, USA
cUniversity of Washington School of Medicine, Seattle, Washington, USA
dDivision of Infectious Diseases, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
eDivision of Infectious Diseases, Department of Medicine, Stanford University, Stanford, California, USA.
Received 16 December, 2009
Revised 7 April, 2010
Accepted 12 April, 2010
Correspondence to Dr Judith J. Lok, PhD, Department of Biostatistics, Harvard School of Public Health, 655 Huntington Avenue Building 2, Room #409, Boston, MA 02115, USA. Tel: +1 617 432 4910; fax: +1 617 432 5619; e-mail: firstname.lastname@example.org