To maximize recovery of acid-fast bacilli from sputum, how often should specimens be collected?

• A. A single morning specimen
• B. A second morning specimen for two days
• C. A first morning specimen for three consecutive days
• D. A midday specimen for two days

Answer: (C)

Maximizing recovery of acid-fast bacilli from sputum relies on collecting multiple specimens on different days because bacilli can be shed intermittently and the concentration is highest in overnight secretions. The first morning specimen is most concentrated since it has had several hours to accumulate in the airway, giving the best chance to detect organisms. Collecting a first morning specimen for three consecutive days combines both higher bacillary load in each sample and repeated sampling to catch variability in shedding, which improves sensitivity compared with a single specimen or specimens collected later in the day.