🔬 Acid-Fast Bacilli (AFB) Smear Test The Acid-Fast Bacilli (AFB) Smear Test (also known as an AFB stain or AFB microscopy) is a rapid, microscopic examination used to detect acid-fast bacteria in patient samples. 🦠 What are Acid-Fast Bacilli? Acid-fast bacilli are a group of bacteria characterized by a waxy cell wall that makes them resistant to decolorization by acids after being stained. The most clinically significant acid-fast bacterium is Mycobacterium tuberculosis, the causative agent of tuberculosis (TB). Other acid-fast organisms include other Mycobacterium species (e.g., non-tuberculous mycobacteria or NTM) and Nocardia species. 📝 How the Test Works Sample Collection: A patient sample suspected of containing AFB is collected. Common samples include: Sputum: Most common for suspected pulmonary TB. Urine Tissue biopsies Cerebrospinal fluid (CSF) Gastric lavage Pleural fluid