Polymerase chain reaction for Mycobacterium tuberculosis complex DNA - Useon negative archival Ziehl-Neelsen cytologic samples

OBJECTIVE: To evaluate the usefulness of a nested polymerase chain reaction (PCR) for Mycobacterium tuberculosis complex on routinely stained cytologi c samples from patients with extrapulmonary tuberculosis. STUDY DESIGN: Nested PCR for the detection of a fragment of the IS IS6110 i nsertion sequence of M tuberculosis complex was applied to Ziehl-Neelsen-ne gative archival cytologic slides of serous effusions (pleural [n = 7], peri toneal [n = 1] and pericardial [n = 1]) and a lymph node fine needle aspira te (n = 1) from nine human immunodeficiency virus (HIV)-positive patients w ith autopsy-proven active extrapulmonary tuberculosis. Malignant effusions and aspirates from nine HIV-positive patients with non-Hodgkin's lymphoma a nd pleural effusions from seven HIV-negative patients with heart failure we re used as controls. DNA was extracted after removing the coverslip and gen tly scraping the cytologic sample from the slides. RESULTS: In all cases, enough DNA was obtained for PCR without any signific ant loss of integrity, as demonstrated by PCR positive for HLA-Dq. PCR for M tuberculosis was positive in 8 of the 10 samples (80%) from patients with tuberculosis but also in three samples (30%) from HIV-positive patients in the control group. None of the samples from the HIV-negative patients was positive. CONCLUSION: PCR for M tuberculosis can be reliably performed on archival cy tologic slides from extrapulmonary samples, but although it is highly sensi tive, it may lead to positive results in immunocompromised patients without any sign of active tubercular disease.