AFB (Tuberculosis) – Sputum Test Sample Type: Sputum Purpose: This test detects acid-fast bacilli (AFB), primarily Mycobacterium tuberculosis, in a sputum sample. It is a key diagnostic tool for pulmonary tuberculosis (TB). About AFB: AFB are a group of bacteria, including Mycobacterium tuberculosis, that resist decolorization by acid-alcohol after being stained—hence the term "acid-fast." TB is transmitted through airborne droplets and mainly affects the lungs. Indications for Testing: Persistent cough lasting more than 2–3 weeks Coughing up blood, chest pain, weight loss, night sweats Suspected or known exposure to tuberculosis Monitoring treatment effectiveness in TB patients Sample Collection & Handling: Early morning sputum samples (usually 3 consecutive days) are ideal. The patient is instructed to cough deeply to produce a specimen from the lungs (not saliva). Samples must be collected in a sterile container and transported promptly. Diagnostic Methods: Ziehl-Neelsen staining for microscopy Fluorescent staining (e.g., auramine-rhodamine) Culture for TB bacteria (more sensitive but takes longer) Molecular tests (e.g., GeneXpert MTB/RIF) for rapid detection and rifampicin resistance Clinical Significance: Positive AFB smear: Likely active TB infection; patient is infectious Negative smear: Does not rule out TB; further testing (culture or molecular) may be needed