An AFB (Acid-Fast Bacilli) detection by smear examination using the ZN (Ziehl-Neelsen) stain on a single sputum sample is a rapid, essential frontline diagnostic test. It is primarily used to detect Mycobacterium tuberculosis, the bacterium responsible for Tuberculosis (TB).


What Do the Terms Mean?
AFB (Acid-Fast Bacilli): "Bacilli" means rod-shaped bacteria. "Acid-fast" refers to a physical property of these bacteria: they have a thick, waxy outer cell wall rich in mycolic acids. Once stained, they resist decolorization by acid-alcohol solutions.

ZN (Ziehl-Neelsen) Stain: A classic, specialized laboratory staining technique designed specifically to penetrate that waxy bacterial cell wall so the bacteria can be seen under a microscope.

Sputum, 1 Sample: Sputum is the thick mucus coughed up from deep within the lungs (not saliva or spit). A "1 sample" test means the diagnosis is being evaluated from a single specimen collection, often a spot sample collected when visiting a clinic or an early morning sample.