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Volume 6 Issue 320 Published - 14:00 UTC 08:00 EST 15-Nov-2004 Next Update - 14:00 UTC 08:00 EST 16-Nov-2004
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Risk factors for early relapse of tuberculosis

In a large study of tuberculosis patients, researchers found that disease relapse was associated with a thrice weekly versus a daily drug therapy regimen and with the presence of cavitation (cavities) on the individual's chest X-ray at diagnosis.

Researchers studied 12,183 patients who completed antituberculosis treatment between January 1, 1998, and December 31, 2000. Of this group, more than 105 cases relapsed within 30 months after commencement of treatment. The mean time to relapse was almost 15 months. A group of 166 controls completed 30 months of follow-up at clinics.

Of those who took the standard 6-month therapy of isoniazid and rifampin supplemented by pyrazinamid for the first 2 months, 61 cases and 140 controls were given daily treatment throughout. A total of 44 cases and 56 control subjects received thrice-weekly treatment. According to the researchers, the definition for relapse refers to situations in which a patient becomes and remains culture negative while receiving antituberculosis drugs, but develops active tuberculosis after completion of treatment.

The investigators pointed out that a better therapeutic efficacy for daily therapy was not surprising because risk factors for relapse are ultimately based on the bacterial load of the lesions. Since M. tuberculosis replicates approximately once daily when it is actively dividing, faster sterilization is expected when actively dividing bacteria are killed daily.

They note that thrice-weekly medications can still be a cost-effective approach when no cavitation is shown on the initial chest X-ray.

When cavities appear, they advise daily, prolonged therapy.

The study appears in the second issue for November 2004 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine.


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