Clinical evaluation of the nelfinavir-rifabutin interaction in patients with tuberculosis and human immunodeficiency virus infection.

STUDY OBJECTIVE: To characterize the bidirectional interaction between twice-daily nelfinavir and twice-weekly rifabutin and isoniazid in patients with tuberculosis and human immunodeficiency virus (HIV) infection. DESIGN: Prospective cohort study. SETTING: Three clinical research centers. PATIENTS: Seven patients with HIV-related tuberculosis. INTERVENTION: Rifabutin 300 mg and isoniazid 15 mg/kg (maximum dose 900 mg) twice/week were administered for at least 2 weeks during the continuation phase of tuberculosis treatment. Antiretroviral therapy with nelfinavir 1250 mg twice/day and two nucleoside reverse transcriptase inhibitors was then added. MEASUREMENTS AND MAIN RESULTS: Patients underwent blood sampling for pharmacokinetic analysis during the continuation phase of tuberculosis therapy and after a median of 21 days after the addition of antiretroviral treatment. When rifabutin was coadministered with nelfinavir, its area under the concentration-time curve from 0-21 hours (AUC(0-21)) increased 22% (geometric mean 5.01 microg.hr/ml [90% confidence interval (CI) 3.25-7.71] with nelfinavir vs 4.10 microg.hr/ml [90% CI 3.18-5.27] without nelfinavir; geometric mean ratio 1.22 [90% CI 0.78-1.92]). Also, the AUC(0-21) for the active metabolite, desacetylrifabutin, increased significantly (geometric mean ratio 3.46, 90% CI 1.84-6.47, p=0.009). In the presence of rifabutin, the pharmacokinetic parameters of nelfinavir and its principal metabolite M8 were similar to those of patients not taking rifabutin. No drug interaction between nelfinavir and isoniazid was detected. CONCLUSIONS: Coadministration of rifabutin and isoniazid without dosage adjustment during twice-weekly tuberculosis therapy with nelfinavir-based antiretroviral therapy resulted in rifabutin exposures within the acceptable ranges for safety and efficacy. Therefore, this combination is an appropriate option for the simultaneous treatment of tuberculosis and HIV infection when tuberculosis therapy is given twice weekly.

Factors associated with loss to follow-up in a large tuberculosis treatment trial (TBTC Study 22).

INTRODUCTION: Loss to follow-up in clinical trials compromises achievement of study goals. We evaluated factors associated with loss to follow-up after completion of treatment phase in a large tuberculosis treatment trial (TBTC/USPHS Study 22) in the U.S. and Canada. METHODS: Patients who were lost to follow-up were compared to those who reached a study end-point or successfully completed follow-up. A generalized estimating equation model was used to combine patient-specific and site-specific factors. RESULTS: Of 1075 patients enrolled, 965 (89.8%) reached a study end-point, died, or completed the 2 year post-treatment follow-up phase, and 110 (10.2%) did not. Multivariate analysis showed the following factors to be independently associated with loss to follow-up: birth outside USA/Canada (OR 2.07, 95% CI 1.25-3.40, p=0.005), history of homelessness (OR 1.94, 95% CI 1.00-3.80, p=0.05), enrollment at a health department (OR 2.71, 95% CI 1.27-5.79, p=0.010), and use of any kind of incentive (cash/cash equivalent) during treatment phase (OR 3.04, 95% CI 1.73-5.33 p=0.0001). CONCLUSIONS: Cultural or linguistic factors and lack of stable housing contribute to loss to follow-up. Attention to these factors could improve long-term retention in clinical trials. Enrollment at a health department and use of incentives during treatment phase may be markers for other factors leading to loss to follow-up.

Quality assurance in a large clinical trials consortium: the experience of the Tuberculosis Trials Consortium.

Quality assurance (QA) is essential for data accuracy and proper evaluation of study objectives in clinical trials. The Tuberculosis Trials Consortium (TBTC)-a collaboration of 28 clinical sites and the Centers for Disease Control and Prevention-has developed a comprehensive QA program that provides quantitative assessments of performance based on clearly defined standards that are communicated to data collectors through a feedback process. The Implementation and Quality Committee of the TBTC developed a Site Evaluation Report (SER) that assesses performance measures (PMs) critical to the accomplishment of study objectives. PMs are defined, quantified, and evaluated, and goals and minimum acceptable scores are specified. Sites not meeting a PM minimum must provide an explanation and develop a plan to meet the goal. Site-specific and system-wide problems can be readily identified through this process. The SER is used prospectively for all TBTC treatment trials, and a Web site has been developed to maximize the availability and usefulness of performance data. The TBTC's comprehensive QA program is an example of a successful method for ensuring high quality, evaluable data.