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Updated: Mar 30, 2026

Diagnosing Pulmonary Tuberculosis with the Xpert MTB/RIF Test
Published on: April 9, 2012
Use of string test and stool specimens to diagnose pulmonary tuberculosis
Andrew R DiNardo1, Andrew Hahn1, Jacinta Leyden2
1Infectious Diseases, Department of Internal Medicine, Baylor College of Medicine, One Baylor Plaza, Mail Stop BCM286, Houston, TX 77030, USA.
Background:
The Xpert MTB/RIF (MTB/RIF) test has advanced the field of tuberculosis (TB) diagnostics; however, depending on age and HIV status, 10-85% of individuals with presumed pulmonary TB (PTB) are unable to produce sputum.
Methods:
The feasibility of using MTB/RIF and culture on stool and string test specimens from 13 adult patients with presumed PTB was studied.
Results:
The string test was well tolerated with a median Wong Baker Faces score of 2. The string test had 100% sensitivity and specificity by MTB/RIF and 87.5% sensitivity and 100% specificity by culture. In stool, Mycobacterium tuberculosis DNA was detected in all cases of culture-confirmed PTB.
Conclusion:
The string test and stool provide diagnostic specimens that warrant further investigation.
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