HOW SHOULD MONITORING AND DRUG SENSITIVITY TESTING BE USED FOR FIRST-LINE TB TREATMENT IN INDIA?

Sunday, January 10, 2016: 09:15
Kai Chong Tong Auditorium, G/F (Jockey Club School of Public Health and Primary Care Building at Prince of Wales Hospital)

Sze-chuan Suen, MS1, Margaret L. Brandeau, PhD1 and Jeremy D. Goldhaber-Fiebert, PhD2, (1)Department of Management Science and Engineering, Stanford University, Stanford, CA, (2)Stanford Health Policy, Centers for Health Policy and Primary Care and Outcomes Research, Department of Medicine, Stanford University, Stanford, CA

Purpose: Patients on first-line tuberculosis (TB) treatment may not be cured if their TB strains are drug-resistant (DR).  However, the sputum-smear (SS) test used for patient monitoring cannot identify bacterial strain, so drug-sensitivity testing (DST) is required to identify such patients for alternative treatment.  Currently, India performs DST in the fourth month of treatment.  We determine the optimal time to administer DST and to identify the patterns of SS results that should prompt DST. If DST is administered too soon, many patients without DR TB will be unnecessarily tested; if administered too late, patients with DR TB may continue to transmit disease and decline in health.  It is critical to determine the optimal timing for DST because India is planning to adopt the fast but expensive Xpert technology system for DST, increasing the cost of unnecessary testing.

Method(s): We formulate a partially observed Markov decision process (POMDP) to determine the optimal timing of SS test information collection and DST. We calculate parameters such as patient response to treatment, dynamics while on treatment (the possibility of default or death), and discounted lifetime costs and health benefits using clinical studies and our previously published TB microsimulation model. We solve the POMDP using value iteration on a constrained feasible belief set.

Result(s): India's current policy appears suboptimal given relatively high national estimates of TB transmission. For these estimated values, DST should be administered to all patients upon initial TB diagnosis. After accounting for averted downstream transmission, we project that this testing sequence could save thousands of dollars per TB patient in discounted net monetary benefits. However, in settings where the risk of transmission is much lower, a patient's SS test result sequence can change the optimal DST timing.  Figure 1 shows the optimal patient testing path in an environment without TB transmission.

Conclusion(s):  India should revise its drug sensitivity testing protocol for the first-line national TB treatment program to provide DST at initial TB diagnosis in areas of average or high drug-resistant TB transmission, and may wish to consider individually tailored DST regimens in low transmission areas to reduce financial costs.

Figure 1: Optimal testing path for patients in no-transmission environments

 

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