What a difference a day makes: same-day vs. 2-day sputum smear microscopy for diagnosing tuberculosis

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Public Health

Background:

• Same-day sputum microscopy is increasingly recommended for tuberculosis (TB) diagnosis.
• Evaluating diagnostic methods in routine programmatic settings is crucial for effective TB control.

Purpose of the Study:

• To compare the diagnostic yield of same-day sputum microscopy versus the conventional 2-day approach for tuberculosis detection.
• To assess the impact of same-day diagnosis on tuberculosis case detection in resource-limited settings.

Main Methods:

• A comparative study involving presumptive TB patients in nine district-level microscopy centers in India.
• Three sputum samples were collected: one on initial visit, one 1 hour later, and one the next morning.
• Ziehl-Neelsen smear microscopy was used, with same-day (spot samples) and 2-day (spot and next-day samples) approaches analyzed.

Main Results:

• The same-day method identified 18.6% of smear-positive cases, while the 2-day method identified 19.7% (P < 0.001).
• The same-day approach missed 6.1% of TB cases, compared to only 0.5% missed by the 2-day method.
• A significant number of tuberculosis cases were missed by the same-day diagnostic strategy.

Conclusions:

• Same-day sputum microscopy for tuberculosis diagnosis resulted in a higher rate of missed cases compared to the 2-day collection method.
• The indiscriminate adoption of same-day diagnosis may impede tuberculosis control efforts in India due to a considerable number of missed cases.
• The study suggests caution in switching to same-day diagnosis when patients reliably attend follow-up testing appointments.