Culturing stool specimens has no added value in diagnosing pulmonary tuberculosis

Area of Science:

• Microbiology
• Infectious Diseases
• Clinical Diagnostics

Background:

• Pulmonary tuberculosis (PTB) diagnosis can be challenging due to difficulties in sputum collection.
• Mycobacterium tuberculosis (Mtb) may be present in stool from swallowed sputum, suggesting stool as a potential alternative specimen.
• Evidence for stool specimen utility in PTB diagnosis is limited, particularly in resource-rich environments.

Purpose of the Study:

• To evaluate the diagnostic utility of stool specimens for detecting Mycobacterium tuberculosis (Mtb) in patients with suspected pulmonary tuberculosis (PTB).
• To assess the feasibility and accuracy of stool culture compared to respiratory specimens for PTB diagnosis in a resource-rich setting.

Main Methods:

• A retrospective analysis of 562 stool specimens collected over two years.
• Comparison of Mtb detection in stool specimens with results from respiratory specimens submitted to a reference laboratory.
• Evaluation of Mtb culture positivity in stool samples from patients diagnosed with PTB.

Main Results:

• Only five out of 19 patients with PTB had Mtb culture-positive stool specimens.
• All stool culture-positive cases also had positive respiratory specimens.
• Sole reliance on stool specimens for PTB diagnosis could lead to missed cases.

Conclusions:

• Stool culture for Mtb has low sensitivity for diagnosing PTB, especially in low-incidence, resource-rich settings like Denmark.
• Stool testing is not recommended as a general diagnostic tool for PTB in such settings.
• Further prospective studies are needed to explore the role of stool analysis in specific subpopulations or settings where sputum collection is difficult.