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Double staining of bacilli and antigen Ag85B improves the accuracy of the pathological diagnosis of pulmonary tuberculosis
  1. Nanying Che,
  2. Yang Qu,
  3. Chen Zhang,
  4. Li Zhang,
  5. Haiqing Zhang
  1. Department of Pathology, Beijing Tuberculosis and Thoracic Tumor Research Institute, Beijing Chest Hospital, Capital Medical University, Beijing, China
  1. Correspondence to Dr Nanying Che, Department of Pathology, Beijing Chest Hospital, 97 Machang, Tongzhou District, Beijing 101149, China; cheny0448{at} Haiqing Zhang, Department of Pathology, Beijing Chest Hospital, 97 Machang, Tongzhou District, Beijing 101149, China;


Background A pathological examination plays an important role in the confirmation of a diagnosis of tuberculosis, especially for smear- and culture-negative cases. However, conventional Ziehl–Neelsen staining and histological tests lack sensitivity and specificity.

Objective To evaluate the diagnostic value of immunohistochemical staining to detect Mycobacterium tuberculosis protein Ag85B and a newly developed double staining (ZC staining) method that can simultaneously detect acid-fast bacilli and M. tuberculosis antigen in the same histological section.

Methods A total of 282 formalin-fixed paraffin-embedded lung tissues were identified following histological examination, including 212 cases of pulmonary tuberculosis and 70 other pulmonary diseases. Ziehl–Neelsen staining, Ag85B-immunohistochemistry and the newly developed ZC staining were performed on serial sections of all the specimens.

Results Expression patterns of Ag85B were consistent with the distribution patterns of acid-fast bacilli. The signal produced by Ag85B-immunohistochemistry was much stronger than that produced by Ziehl–Neelsen staining. The sensitivity of Ag85B-immunohistochemistry was significantly higher than that of Ziehl–Neelsen staining, 53.8% (95% CI 47.0% to 60.5%) vs 34.4% (95% CI 28.0% to 40.9%). The newly developed ZC staining, integrating advantages of both Ziehl–Neelsen staining and immunohistochemistry, further improved the rate of sensitivity up to 65.6% (95% CI 59.1% to 72.0%).

Conclusions This new method, detecting both acid-fast bacilli and M. tuberculosis antigen, is a simple and sensitive method for the pathological diagnosis of tuberculosis and can be easily incorporated into routine tests of pathological laboratories.


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