Utility of papanicolaou stain-induced fluorescence in the cytodiagnosis of extrapulmonary tuberculosis.

OBJECTIVE: To study the utility of Papanicolaou stain-induced fluorescence (PIF) in the detection of tubercle bacilli and to compare its diagnostic efficacy with that of the conventional Ziehl-Neelsen (ZN) method.

STUDY DESIGN: This prospective study was carried out at a tertiary health care center, over a period of 2 years between January 2001 and December 2002. A total of 500 cases offine needle aspiration cytology from lymph nodes and other extrapulmonary sites were studied. Only cases that were clinically and cytologically suggestive of tuberculosis were included in the study. The smears were stained with ZN and Papanicolaou stain and examined under light and fluorescence microscopes, respectively for detection of acid-fast bacilli (AFB). Mycobacterial culture was used as the gold standard to compare the results.

RESULTS: Cytologic smears were categorized into 4 distinct cytomorphologic patterns: epithelioid granulomas without caseous necrosis (101 cases), epithelioid granulomas with caseous necrosis (268 cases), caseation or acute inflammatory exudate only (114 cases), and occasional epithelioid cells without necrosis or giant cells (17 cases). The overall AFB positivity was 30.8% with the ZN method, while it was 40.6% with PIF. Moreover, PIF was more effective in detecting bacilli in group I lesions (18.8% vs. 6.9% with ZN method), in which the bacillary load is very low.

CONCLUSION: PIF is superior to the conventional ZN method in detecting tubercle bacilli, particularly when the bacillary load is low. It is a relatively inexpensive and fast technique.