MID for analyzing the cost-effectiveness of two therapies for HIV:

- monotherapy, which means "only zidovudine".

- combined therapy, which means "zidovudine plus lamivudine for the first three years (i.e., three cycles), then zidovudine alone".

Original paper:

Chancellor JV, et al.

Modelling the cost effectiveness of lamivudine/zidovudine combination therapy in HIV infection.

Pharmacoeconomics 1997;12:54-66.

There is another MID that faithfully replicates the Excel version of this model built by A. Briggs--see www.probmodelxml.org/networks/mid/MID-Chancellor.pgmx.

That MID was built by Iñigo Bermejo and F. Javier Díez in July 2013. This new MID is the result of the revision done by F. J. Díez in June 2016.

Open the properties dialog of each node to obtain additional information. See also the chapter on MIDs in OpenMarkov's tutorial.

]]>

Health state of the VIH patient: State A (200<cd4 cells/mm3<500); State B (cd4<200); State C (AIDs); Death

]]> 1.0 1.0 0.01 0.01 0.01 0.01

In Chancellor's model, the effect of combined therapy is represented by a reduction of the relative risk of progressing to more severe degrees of the disease, as explained in section "Clinical efficay" of their paper. In this model, this effect is modelled by assuming that combined therapy sometimes inhibit the transitions, with a probability equal to the relative risk.

]]> 0.01 State A 1.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 0.2498570612 0.7501429388 0.0 0.0 0.0 1.0 0.0 0.0 0.0119236884 0.4069952305 0.5810810811 0.0 0.0 0.0 1.0 0.0 0.0098039216 0.0668973472 0.2018454441 0.7214532872 0.0 0.0 0.0 1.0 437.0 1312.0 1.0 0.0 0.0 15.0 512.0 731.0 0.0 17.0 116.0 350.0 1251.0 0.0 0.0 2278.0 1.0 0.0 0.0 6948.0 1774.0 1701.0 6948.0 6948.0 1774.0 1774.0 1701.0 1701.0 0.0 2059.0 1278.0 1055.0 2059.0 2059.0 1278.0 1278.0 1055.0 1055.0 none monotherapy combination therapy monotherapy The probability of inhibiting the transition is 0.509, the same as the relative risk of combined therapy with respect to monotherapy. This value, as well, as the 95% confidence interval 0.365-0.710, appear in Table IV of the paper by Chancellor et al. They are taken from a meta-analysis: Staszewski et al. Reductions in HIV-1 disease progression for zidovudine/lamivudine relative to control treatments: a meta-analysis of controlled trials. AIDS, 1997, 11:477-83. The difference of this MID with the Excel version of the same model is that the second-order distribution for this parameter is not modelled with a log-normal distribution, which might lead to transition probabilities below 0 or above 1, but with a Beta. ]]> 1.0 0.0 1.0 0.0 0.4909999056 0.5090000944 1.0 17.62564 17.00233 0.0 0.0 2085.50445 COST_EFFECTIVENESS 1 END