The optimal tissue thickness for histological diagnosis of tuberculosis / Dr. Aida Nurbaiti Arbain

Introduction. Tuberculosis is an important infectious disease caused by the bacillus Mycobacterium tuberculosis. It can cause pulmonary and extrapulmonary tuberculosis. There are several acid-fast bacilli (AFB) stains available for the formalin fixed paraffin embedded specimens. These include Kinyoun stain, a faster and cheaper option for diagnosing tuberculosis on tissue specimens. There is no available published study on the optimal tissue thickness for AFB staining; hence this study was conducted to find the best thickness in facilitating AFB detection.
Materials and methods. This is a retrospective study. A total of 84 granuloma cases were included, of which 29 cases were positive for Mycobacterium Tuberculosis culture and another 55 cases were negative. All cases were subjected to Kinyoun stain at 3 microns, 5 microns and 7 microns thick sections for AFB detection. The AFB detection was done by the researcher and followed by I 0% random screening by two pathologists. The sensitivity, specificity, positive predictive value and negative predictive value of each thickness were calculated and compared.
Results. In this study, 7 microns thickness shows the highest sensitivity (48.26%) compared to the 3 microns (31.03%) and 5 microns thickness (37.93%). 7 microns thickness also shows higher specificity than 5 microns thickness (92.73%) and this result is similar to 3 microns thickness.
Conclusion. The 7 microns thick section yielded the highest sensitivity in detecting AFB using Kinyoun stain.