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Time to sputum culture conversion in multidrug-resistant tuberculosis:
Predictors and relationship to treatment outcome.
Annals of Internal Medicine 2006; 144(9):650-659.
Holtz TH, Sternberg M, Kammerer S, Laserson KF, Riekstina V, Zarovska
E, Skirpconoka V, Wells CD, Leimane V.
Abstract
BACKGROUND: Conversion of sputum mycobacterial cultures from positive growth
to negative growth of Mycobacterium tuberculosis in patients with pulmonary
tuberculosis (TB) is considered the most important interim indicator of the
efficacy of anti-TB pharmacologic treatment for multidrug-resistant disease.
OBJECTIVE: To evaluate and compare time to and predictors of initial sputum
culture conversion with predictors of treatment outcome for patients with
multidrug-resistant TB. DESIGN: Retrospective cohort study. SETTING: Latvia.
PATIENTS: All civilian patients with multidrug-resistant TB treated with
the DOTS-Plus strategy between 1 January and 31 December 2000. INTERVENTION:
Individualized treatment for confirmed sputum culture-positive pulmonary
multidrug-resistant TB. MEASUREMENTS: Time to initial sputum culture conversion
and treatment outcome. RESULTS: Among 167 patients who were sputum culture-positive
at initiation of second-line therapy, 129 (77%) converted in a median time
of 60 days (range, 4 to 462 days) and 38 (23%) did not convert. Independent
predictors of a longer sputum culture conversion time, using an accelerated
failure time regression model, included previous treatment for multidrug-resistant
TB, high initial sputum culture colony count, bilateral cavitations on chest
radiography, and the number of drugs the initial isolate was resistant to
at treatment initiation. Treatment outcomes were statistically significantly
worse for patients who did not convert their sputum culture within 2 months.
LIMITATIONS: Twenty-five percent of patients missed 5 or more monthly sputum
collections. CONCLUSIONS: Under program conditions in Latvia, most patients
with multidrug-resistant TB achieved sputum culture conversion within 12
weeks of starting treatment. Chest radiography and sputum culture drug susceptibility
testing can assist physicians in predicting which patients will convert more
slowly. Sputum culture conversion is a useful and appropriate interim indicator
of treatment outcome in patients with multidrug-resistant TB.