The AFB/ZN Stain is the essential, rapid first-look test for Tuberculosis (TB). 'AFB' stands for Acid-Fast Bacilli, the specific group of bacteria that includes TB. The 'ZN' (Ziehl-Neelsen) stain is the special dye we use to make these bacteria visible under a microscope. If you have a persistent cough or are at risk for TB, this test is the critical first step. It requires a simple sputum (phlegm) sample, usually collected in the morning. While a TB culture is needed for a final, definitive diagnosis, this rapid smear test provides the fast, preliminary answer your doctor needs to begin your care and ensure public safety.