## Table 2 |
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Probability change scenarios |
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Probability of change in disease state from lower CD4 range to next higher (see Figure2) |
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Effectiveness of Intervention | p(t) x_{1} |
p(t) x_{2} |
p(t) x_{3} |
p(t) x_{4} |
Average |

Minimally | 5% | 0% | 0% | 0% | 1% |

Slightly | 5% | 1% | 0% | 0% | 2% |

Moderately | 10% | 5% | 5% | 0% | 5% |

Highly | 20% | 10% | 5% | 0% | 9% |

*Note:* Each *p* represents an assumed probability that the intervention would increase a patient’s
CD4 count sufficiently that they would move to the next higher CD4 group (see Figure 2). The expression *t* in parentheses indicates that the probability refers to a transition, while each
*x* with a subscript indicates which of the four possible transitions is represented.
For the minimally effective scenario, the probability represented as “*p*(t) x_{1}” thus indicates that there is a 5% chance that a person in the lower group might
move to the next higher group. The average column is the mean of the probabilities
for each possible change in CD4 and was used for estimation of changes in costs and
utilities.

Ownby * et al.*

Ownby * et al.* *BMC Medical Informatics and Decision Making* 2013 **13**:29 doi:10.1186/1472-6947-13-29