Detection of Mycobacterium tuberculosis by Polymerase Chain Reaction With DNA Eluted From Aspirate Smears of Tuberculous Lymphadenitis

Abstract

We have developed and evaluated a polymerase chain reaction (PCR) assay suitable for the detection of Mycobacterium tuberculosis DNA from fine needle aspirate smears of patients with tuberculous lymphadenitis. Air-dried fine needle aspirates of cervical lymph nodes from 98 patients with tuberculous lymphadenitis were studied for cytomorphology, detection of acid fast bacilli by Ziehl-Neelsen staining, culture and nested PCR with IS6110 for mycobacteria on DNA eluted from the dried unstained cytology smear. Twenty aspirate smears with diseases other than tuberculosis were similarly tested as controls. Mycobacterial-DNA was amplified by PCR in 84 (85%) cases and in 1 (5%) control. The mycobacteria could be detected by Ziehl-Neelsen stain and culture in 15 (15.3%) and 24 (24.4%) cases, respectively, whereas both tests were negative in controls. When results were compared with nested PCR on DNA from biopsies from the same case as the gold standard, the sensitivity, specificity, positive and negative predictive values of smear PCR were 85%, 95%, 96%, and 59%, respectively. In conclusion, PCR using dried cytology smear material is feasible and is a simple and sensitive technique for an early and specific diagnosis of M. tuberculosis complex. This is particularly useful when cytology is equivocal and can obviate the use of more invasive procedures.