Correlation of Cytology-Positive Tuberculosis with TB PCR: A Prospective Observational Study

Abstract

Background: Cytological identification of granulomatous inflammation is widely used for the diagnosis of tuberculosis, particularly in extrapulmonary cases. However, cytology alone cannot provide definitive etiological confirmation, and Ziehl–Neelsen staining often shows low sensitivity. Molecular techniques such as tuberculosis polymerase chain reaction (TB PCR) enable rapid and sensitive detection of Mycobacterium tuberculosis and may complement cytological diagnosis.

Objective: To evaluate the correlation between cytology-positive granulomatous lesions suggestive of tuberculosis and TB PCR results.

Methods: This prospective observational study was conducted in the Department of Pathology & microbiology, Patna Medical College and Hospital, Patna, from August 2024 to December 2025. A total of 135 patients with cytological evidence of granulomatous inflammation on fine-needle aspiration cytology were included. Cytological findings were assessed using May–Grünwald–Giemsa and Ziehl–Neelsen staining. Samples were subsequently subjected to TB PCR for detection of Mycobacterium tuberculosis complex DNA. Cytology findings were correlated with TB PCR results, and statistical analysis was performed to assess diagnostic agreement.

Results: TB PCR detected Mycobacterium tuberculosis DNA in a significant proportion of cytology-positive cases. Higher PCR positivity was observed in lesions showing granulomas with necrosis compared to those without necrosis. TB PCR demonstrated additional diagnostic value in cytology-positive but Ziehl–Neelsen–negative cases. A statistically significant correlation was found between cytological features suggestive of tuberculosis and TB PCR positivity.

Conclusion: There is a significant correlation between cytology-positive granulomatous lesions and TB PCR results. TB PCR serves as a valuable adjunct to cytology by improving diagnostic confirmation, particularly in smear-negative cases. The combined use of cytology and molecular testing enhances diagnostic accuracy for tuberculosis in high-burden settings.

Keywords: Tuberculosis; Granulomatous inflammation; Fine-needle aspiration cytology; TB PCR; Extrapulmonary tuberculosis