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Home / The International Journal of Tuberculosis and Lung Disease, Volume 19, Number 5

Intra-gastric string test: an effective tool for diagnosing tuberculosis in adults unable to produce sputum

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SETTING: Tuberculosis (TB) diagnosis is challenging in patients who are unable to produce sputum. The string test, a method for retrieving enteropathogens, is a potential alternative diagnostic tool.

OBJECTIVES: To compare the TB detection yield and tolerability of the string test and that of sputum induction in adults with presumed TB in Uganda.

DESIGN: Cross-sectional study. String test and sputum induction were performed consecutively in patients unable to produce sputum. The string was removed after a 2-h intra-gastric downtime. Sputum induction used nebulised 5% saline for 20 min. Light-emitting diode fluorescence microscopy, Löwenstein-Jensen and MGIT culture were performed on all specimens, and the Xpert® MTB/RIF assay on a subset. Tolerability questionnaires were administered.

RESULTS: Of 210 patients included in the study, 59% were human immunodeficiency virus (HIV) positive and 50 (23.8%) were diagnosed with TB. Of these, 48 (96.0%) were detected with the string test and 46 (92.0%) with sputum induction. In patients with specimens collected using both methods for paired analysis, the yield of microscopy detection with the string test was 13.8% (26/188) vs. 13.3% (25/188) with sputum induction (P = 1.0). The yield increased to 22.9% (42/183) using culture for string test vs. 24.6% (45/183) for sputum induction (P = 0.37). Xpert detected TB in 15/96 (15.6%) patients with the string test vs. 17/96 (17.7%) with sputum induction (P = 0.62). Tolerability was comparable.

CONCLUSION: The string test was well tolerated and provided similar yields to sputum induction, offering a viable alternative in resource-limited settings with minimal risk of transmission.

Keywords: detection; diagnosis; mycobacterial disease; specimen collection

Document Type: Research Article

Affiliations: 1: *Epicentre Mbarara Research Centre, Mbarara, Uganda 2: †Epicentre, Paris, France 3: ‡Mbarara University of Science and Technology, Mbarara, Uganda

Publication date: 01 May 2015

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  • The International Journal of Tuberculosis and Lung Disease (IJTLD) is for clinical research and epidemiological studies on lung health, including articles on TB, TB-HIV and respiratory diseases such as COVID-19, asthma, COPD, child lung health and the hazards of tobacco and air pollution. Individuals and institutes can subscribe to the IJTLD online or in print – simply email us at [email protected] for details.

    The IJTLD is dedicated to understanding lung disease and to the dissemination of knowledge leading to better lung health. To allow us to share scientific research as rapidly as possible, the IJTLD is fast-tracking the publication of certain articles as preprints prior to their publication. Read fast-track articles.

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