What Is the Urine Acid-Fast Bacilli Test?

The AFB test identifies bacteria that don't decolorize with acid-alcohol during staining, hence called acid-fast. This unique property is characteristic of Mycobacterium species — the culprits behind tuberculosis and similar infections. Urine samples are examined microscopically after special staining to detect these bacteria, or cultured to encourage their growth and confirm diagnosis.

Why Is the Test Done?

• To diagnose genitourinary tuberculosis in patients suspected of having infections affecting kidneys, bladder, or urinary tract

• To monitor treatment efficacy in urinary TB cases

• To differentiate tuberculosis from other urinary tract infections

How Is the Test Performed?

• A clean-catch midstream urine sample or catheterized urine is collected, sometimes over multiple consecutive days to improve detection sensitivity
• Samples undergo AFB staining and microscopic examination
• Culture methods may be used to grow bacteria, though results take longer (up to several weeks)
• Advanced molecular techniques like PCR may also be applied for quicker and more sensitive detection

What to Expect?

The test is non-invasive but requires proper urine collection and timely submission to the lab. Because urinary TB may be intermittent, multiple samples increase accuracy. Early detection via the AFB urine test is crucial for initiating effective antibiotic therapy and preventing complications.