Estimation of the CD4 cells recovery probability following long term HAART in HIV positive patients using a non-homogenous Markov model

Introduction: Previous studies found highly active antiretroviral therapy (HAART) to be associated with improved survival among human immunodeficiency virus (HIV) infected peoples. The longer someone’s CD4 cell count remains low, the higher the risk of complications including those due to AIDS events or Opportunistic infections.  Therefore, monitoring patients to maintain their high level of immune deficiency is important.

Methods: One hundred and three HIV infected patients who had already initiated HAART undergone a longitudinal investigation from the April 1995. A non-homogenous Markov model was used to estimate the probability of CD4 cells recovery in these patients.

Results: Eighteen patients died during the study treatment. Hazard ratio of recovery from state 2 of immune deficiency to state 1 is 3 times ((1.66, 5.19) 95% confidence interval) at 65 month after initiating HAART compared to before it. This parameter for recovery from state 3 to 2 was 0.3 with (0.11, 0.73) 95% confidence interval. If a patient remains at state 2 for more than 65 months after the treatment initiation the probability of recovery to state 1 was more than 55 percent. 

Conclusion: The use of HAART was effective in recovering the CD4 cells count especially when a patient remains in better immune state for long years. Our findings were in line with WHO guidelines on HAART which recommend initiating HAART at CD4 cell counts of 350–499 cells/ml.