AFB- Detection of DNA- Tb PCR Any Specimen Except Blood in Dehradun

What is a AFB- Detection of DNA- Tb PCR Any Specimen Except Blood?

This is tuberculosis DNA detection applied to whatever specimen the disease is suspected in, other than blood. That breadth is the point, because extrapulmonary tuberculosis is common in India and is genuinely difficult to diagnose. Tuberculosis affecting lymph nodes, the pleura, the abdomen, bone and joints, the spine, the kidney or the nervous system typically involves very small numbers of organisms, so smear microscopy is usually negative and culture, already slow, frequently fails to grow anything even in confirmed disease. Molecular detection is considerably more sensitive in that setting and returns a result in a day or two rather than weeks. The specimen matters as much as the test: lymph node aspirate or biopsy, pleural or ascitic fluid, cerebrospinal fluid, pus, urine, synovial fluid or tissue, each collected by a doctor by the appropriate route. Blood is excluded because circulating organisms are rare outside disseminated disease. The same caveat applies as for any TB PCR: it detects DNA irrespective of viability, so it cannot judge treatment response, and a negative result in low-load disease does not exclude tuberculosis.

Why take this test?

This test is advised where tuberculosis outside the lungs is suspected: a persistently enlarged lymph node, particularly in the neck, an unexplained pleural effusion or ascites, chronic back pain with vertebral changes on imaging, a swollen joint, sterile pyuria where urine shows white cells but no bacteria grow, or unexplained meningitis with a lymphocyte-predominant cerebrospinal fluid. It is used alongside the other findings on the same specimen, since a fluid analysis showing lymphocyte predominance with a high protein and a raised ADA builds the case even when the organism is not found. It is also used where a biopsy has shown granulomas and confirmation is wanted. The specimen must be collected by a doctor through the appropriate procedure, so this is not a test you arrange independently. Where resistance is a concern, discuss an assay that reports rifampicin resistance at the same time.

• A persistently enlarged lymph node, especially in the neck
• Unexplained pleural effusion or ascites
• Chronic back pain with vertebral changes on imaging
• A chronically swollen joint
• Sterile pyuria, with white cells in urine but no growth
• Unexplained lymphocytic meningitis, or granulomas found on biopsy

FAQs: AFB- Detection of DNA- Tb PCR Any Specimen Except Blood in Dehradun