Rabies diagnosis relies on testing which tissue?

• A. Brain tissue
• B. Blood
• C. Saliva
• D. Urine

Answer: (A)

The key idea is that rabies concentrates in the central nervous system, so the most reliable way to confirm infection is by testing brain tissue. In diagnosing rabies, labs look for rabies virus antigen or viral RNA directly in brain tissue, typically using the direct fluorescent antibody test or RT-PCR on samples from the brainstem and surrounding CNS tissue. This provides the highest sensitivity and specificity because the virus replicates and accumulates in neural tissue.

Other samples like blood, saliva, or urine may be tested, but they’re not dependable for a definitive diagnosis in most cases since the virus is not consistently present in those fluids and levels can be low or intermittent. That’s why brain tissue is the standard tissue used for confirmation.