Sputum smear microscopy in DOTS: Are three samples necessary? An analysis and its implications in tuberculosis...

Area of Science:

• Microbiology
• Pulmonary Medicine
• Public Health

Background:

• Tuberculosis (TB) diagnosis relies heavily on smear microscopy.
• The Directly Observed Treatment Short-course (DOTS) strategy is a cornerstone of global TB control.
• Optimizing diagnostic methods within DOTS is crucial for efficient case detection.

Purpose of the Study:

• To evaluate the diagnostic relevance of the spot-morning-spot (SMS) smear microscopy method.
• To assess the contribution of additional sputum samples in TB diagnosis within DOTS.
• To determine the efficiency of TB case detection using simplified microscopy protocols.

Main Methods:

• Retrospective analysis of smear microscopy results from 546 pulmonary tuberculosis cases.
• Utilized data from a dedicated DOTS center.
• Compared diagnostic yield across three sputum sample types: spot, morning, and a second spot sample.

Main Results:

• 82% of cases showed positive Acid-Fast Bacilli (AFB) in all three analyzed sputum samples.
• 98% of cases were diagnosed by examining either the morning sample alone or the combination of spot and morning samples.
• The second spot sample yielded positive results in only 2% of cases, indicating limited additional diagnostic value.

Conclusions:

• The examination of a third sputum sample, particularly a second spot sample, offers minimal additional diagnostic yield in TB detection.
• A simplified approach using one spot and one early morning sputum sample can accurately diagnose 98% of pulmonary TB cases.
• This finding has significant implications for streamlining diagnostic procedures and enhancing the efficiency of DOTS programs.