Cost effectiveness analysis of recurrent events
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Author: Xuanqian Xie For the project of cost-effectiveness analysis of Mitomycin after Transurethral Resection of Bladde

Author: Xuanqian Xie

For the project of cost-effectiveness analysis of Mitomycin after Transurethral Resection of Bladder Tumor, initially I planned a regular Markov model to estimate the QALY and/or life years. See Figure 1. Briefly, after operation at time zero, patients are disease free, and then they may experience recurrence, disease progression, or death over time.


But, after a discussion with coauthors, we decide to focus on the recurrence only (non-muscle invasive bladder cancer), as cancer progression and death may be less relevant with Mitomycin therapy. Thus, we re-constructed the following model. (See Figure 2).The details of the assumptions of this model and results can be found in the original publication (Feifer et al. 2010).

The other example was based on the probiotics project (Sinclair et al. 2011). (Our report did not include the economic analysis finally for the relatively weak clinical evidences supporting probiotics.) The primary outcome of this economic study is the cost per CDAD case avoided by using probiotics. Only costs relevant to CDAD therapy were included. We followed simulated individuals for 1 year from the date taking antibiotics.


1. Probiotics can reduce the risks of the initial episode of CDAD, but it does not have any further effect for recurrence of CDAD.

2. When suffering CDAD, two arms patients (probiotics vs. non-probiotics) would be treated identically.

3. Probiotics does not impact the severity levels of CDI.

4. The real treatments for CDI are very complex. For simplicity, we assume that for mild-moderate CDI patients, if they are not cured by Metronidazole for 10-14 days, they would be cured by Vancomycin.

5. We do not distinguish the relapse or re-infection of CDI.

6. The treatments for the first and subsequent recurrences are different. In our model, the recurrence includes all recurrences, and does not distinguish first or subsequent recurrences. For simplicity, we suppose XX% would be treated by oral/ intravenous Metronidazole/ Vancomycin. The length of stay in recurrence would be same as initial episode of CDI. And all patients would be cured in first treatment for recurrence.

7. No patients die for the recurrence of CDI. (It is not easy to estimate the attributable mortality rate.)

8. Patients move out of this model (or stop running), when they do not have CDI, mortality, no recurrence, etc. And all patients were censored in 1 year.




Feifer A, Xie X, Brophy JM, Segal R, Kassouf W. Contemporary Cost Analysis of Single Instillation of Mitomycin after Transurethral Resection of Bladder Tumor in a Universal Health Care System. Urology 2010; 76(3): 652-7.  Link:

Sinclair A, Xie X, Dendukuri N. The Use of Lactobacillus probiotics in the Prevention of Antibiotic Associated Clostridium Difficile Diarrhea. Montreal (Canada): Technology Assessment Unit (TAU) of the McGill University Health Centre (MUHC); 2011 Dec 19. Report no. 54. 45 p. Available from: 54_probiotic.pdf