MicrobiologyInfectious Disease

AFB Culture & Sensitivity (Radiometric)

Normal Range
No Growth
Sample Type
Sputum
Fasting
No
Unit
Qualitative

Function

AFB (Acid-Fast Bacilli) Culture and Sensitivity is the gold standard for diagnosing infections caused by Mycobacterium species, most notably Mycobacterium tuberculosis. The radiometric method (like BACTEC) uses a liquid medium containing radio-labeled substrates to detect the growth of bacteria much faster (1-2 weeks) than traditional solid media (4-8 weeks).

Why it is Ordered

This test is ordered for patients with symptoms of Tuberculosis (TB), such as chronic cough, weight loss, and night sweats, or for those with abnormal chest X-rays. The 'Sensitivity' portion is critical; it tests which antibiotics successfully kill the specific strain of bacteria isolated, ensuring the patient is not treated with drugs to which the bacteria are resistant.

Associated Conditions

  • Pulmonary Tuberculosis: The most common form of TB affecting the lungs.
  • Extrapulmonary TB: Infection in the kidneys, spine, or lymph nodes.
  • Non-Tuberculous Mycobacteria (NTM): Environmental bacteria that can cause lung disease in immunocompromised individuals.
  • MDR-TB: Multi-drug resistant tuberculosis strains.

Why Context Matters

Sputum samples can be easily contaminated with oral bacteria if the mouth isn't rinsed properly. Furthermore, if a patient has already started antibiotics before the sample is collected, it can result in a false negative (no growth), even if an infection is present. Multiple samples over different days are often required for accuracy.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for AFB Culture & Sensitivity (Radiometric):

Research & Guidelines

Related Indicators

Albert's Stain

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Spore Stain

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AFB Culture (Radiometric)

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DR

Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

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