A Natural History Study of Tuberculosis in China; Correlates of a Successful Response to Treatment

Despite optimal antimicrobial treatment with directly observed short-course therapy (DOTS), about 5-10 percent of drug-compliant patients with cured tuberculosis (TB or MTB) relapse, usually within a year after completion of therapy. This percentage is even greater for patients that have previously been treated for TB who often are infected with multi-drug resistant (MDR) and extensively drug resistant (XDR) organisms. The People s Republic of China has the second highest number of cases of TB in the world, with a rate of 101 cases/100,000 person-years estimated for 2004. Based on the data of the 4th national TB epidemiological survey in 2000, it is estimated that there were 1.96 million instances of pulmonary TB. With an established MDR TB prevalence of 10.7 percent, there were an estimated 209,720 cases of pulmonary, bacteriology confirmed MDR TB in China in 2000. About half of all prevalent cases of TB disease in 2000 were extrapulmonary.

This prospective longitudinal natural history study will monitor 150 subjects with suspected TB at the Henan Provincial Chest Hospital during their initial response to antituberculous chemotherapy. The subjects will be divided into 3 groups of TB-infected individuals: Cohort A) acid-fast bacilli (AFB) smear positive pulmonary disease; Cohort B) smear negative pulmonary disease; and Cohort C) extra-pulmonary disease (EPTB) in order to reflect the spectrum of TB manifestations observed at Henan Provincial Chest Hospital. We will also be enrolling 45 non-TB suspects as controls (Cohort D). The control group will serve as a comparison group for exploratory immunologic and diagnostic assays that may, in the future, serve as ways to diagnose TB and/or evaluate response to therapy.

In this exploratory study, we will be looking at the change in total volume of disease as detected by computerized tomography scans of the chest at baseline, at 2 months, and at 6 months. We will also be looking at scanned regions of extrapulmonary TB. In addition, we will monitor chemotherapeutic regimen, changes in the host immune response, overall changes in clinical parameters, initial and acquired drug-resistance of the infecting isolates, and changes in bacterial and host markers in subject samples during chemotherapy. In each case, we will look for associations of these parameters with rates of disease resolution correlated with specific structural features determined by computerized tomography scanning of the sites of TB disease (with the exception of TB meningitis and cutaneous TB, for which there are no specific lesions to follow radiographically). These studies will allow us to evaluate the use of entry criteria in future clinical trials and eventual TB diagnosis confirmation using these entry categorizations. We will also be able to examine the impact of initial regimen selection, and subsequent modifications, mycobacterial strain characteristics, extent of disease, types of lesions and host immunologic response to the overall outcome of chemotherapy, as well as potentially identify surrogate markers for improving monitoring of the response to chemotherapy.