PCR diagnosis on formalin-fixed, paraffin-embedded tissues with acid-fast stain and culture negativity in chronic dialysis patients of cervico-mediastinal tuberculous lymphadenitis.

BACKGROUND: Bacteriologic studies often provide negative results in tuberculous infection, and do not favour early diagnosis. Polymerase chain reaction (PCR) is known to diagnose tuberculosis quickly. With this in mind, we used PCR to detect mycobacterial DNA on formalin-fixed, paraffin-embedded tissues with acid-fast stain and culture negativity in two dialysis patients with cervico-mediastinal lymphadenopathy.
METHODS: Sections of neck lymph nodes were cut at two different levels. At each level, two semi-adjacent sections with a thickness of 5 microm each were cut using standard microtomes with disposable blades. The first section mounted on a glass slide was stained by Ziehl-Neelsen, and the second section was examined by PCR based on a 123 bp fragment of IS6110 that is specific for the Mycobacterium tuberculosis complex.
RESULTS: The histology of lymph nodes disclosed inflammatory necrotizing granulomas, but acid-fast stain for M. tuberculosis was negative in the two patients. DNA of M. tuberculosis was detected in lymph node samples from each patient by PCR on the IS6110 element and by dot-blot hybridization.
CONCLUSIONS: PCR assay is a potentially useful approach for early and rapid diagnosis of tuberculous lymphadenitis in chronic dialysis patients, since mycobacterial staining and culture often provide negative results.