An AFB smear (acid-fast bacilli smear) is a microscopic test where respiratory or other clinical specimens are stained (e.g., Ziehl–Neelsen) and examined for acid-fast organisms, notably Mycobacterium tuberculosis. It’s a rapid, inexpensive screening tool for active, potentially infectious TB; however, it’s less sensitive than culture or molecular tests and needs confirmatory testing and clinical correlation.

A TB smear test (sputum smear microscopy) examines coughed-up sputum under a microscope after special staining to detect acid-fast bacilli. It’s a rapid, inexpensive way to diagnose pulmonary TB and assess infectiousness, usually requiring multiple early-morning samples. Smear microscopy is less sensitive than culture or molecular tests, so negative smears may need further testing for confirmation and drug-resistance assessment.

Collect early‑morning sputum by rinsing your mouth with water, then coughing deeply to bring up secretions from the chest (not saliva). Expectorate 2–5 mL into a sterile, leak‑proof container. Provide 2–3 specimens on consecutive days (or as instructed). Label and deliver samples promptly. Avoid eating or smoking before collection and follow infection‑control instructions (masking and hand hygiene).

AFB positive means acid‑fast bacilli (mycobacteria) were seen in a clinical specimen, suggesting a mycobacterial infection such as tuberculosis or non‑tuberculous mycobacteria. It often indicates active infection and potential contagiousness, but doesn’t identify the exact species or drug resistance. Additional tests (culture, molecular assays) are needed to confirm the organism and guide treatment and infection‑control measures.

An AFB (acid-fast bacilli) smear detects mycobacteria in specimens but does not definitively confirm tuberculosis. A positive AFB suggests a mycobacterial infection, but cannot reliably distinguish M. tuberculosis from non‑tuberculous mycobacteria. Confirmation requires culture or molecular tests (NAAT/PCR) and drug susceptibility testing. A negative smear does not rule out TB; more sensitive tests and clinical evaluation are needed.

Smear-negative pulmonary tuberculosis is TB with negative sputum smear microscopy for acid-fast bacilli despite clinical or radiological signs of TB or positive culture/molecular tests. It’s often less infectious than smear-positive disease but can still transmit. Common in early or paucibacillary disease, children, and people with HIV. Diagnosis uses chest X-ray, GeneXpert/culture, and clinical assessment; treatment follows standard TB regimens.