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The Optimal Time to Initiate HIV Therapy Under Ordered Health States

Operations and Logistics Division, Sauder School of Business, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z2
Department of Management, Bucknell University, Lewisburg, Pennsylvania 17837
Department of Industrial Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
Section of Decision Sciences and Clinical Systems Modeling, Department of Medicine, Department of Health Policy and Management, Department of Industrial Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15213
steven.shechter{at}sauder.ubc.ca
matt.bailey{at}bucknell.edu
schaefer{at}ie.pitt.edu
robertsm{at}msx.upmc.edu

The question of when to initiate HIV treatment is considered the most important question in HIV care today. Benefits of delaying therapy include avoiding the negative side effects and toxicities associated with the drugs, delaying selective pressures that induce the development of resistant strains of the virus, and preserving a limited number of treatment options. On the other hand, the risks of delayed therapy include the possibility of irreversible damage to the immune system, development of AIDS-related complications, and death. We use Markov decision processes to develop the first HIV optimization models that aim to maximize the expected lifetime or quality-adjusted lifetime of a patient. We prove conditions that establish structural properties of the optimal solution and compare them to our data and results. Model solutions, based on clinical data, support a strategy of treating HIV earlier in its course as opposed to recent trends toward treating it later.

Subject classifications: dynamic programming; Markov decision processes; health-care treatment; HIV/AIDS; stochastic modeling applications.
History: Received December 2005; revision received July 2007; accepted July 2007.