Agreement Test of Histopathology in the Diagnosis of Extrapulmonary Tuberculosis with Gold Standard Polymerase Chain Reaction Technique: A Step to Overcome False Diagnosis

Abstract

BACKGROUND: Tuberculosis (TB) is global health problem which is caused by Mycobacterium tuberculosis (M. tuberculosis) bacteria. One-quarter of the world’s populations is infected by M. tuberculosis and only 10–15% of those develop the disease, while the remaining 85–95% of the population are carrying the bacteria and cannot transmit the disease to the others. M. tuberculosis bacteria affects the lungs, but any organ in the body can be affected by the bacteria. About 15% of M. tuberculosis infections are of in the extrapulmonary type. The diagnosis of extrapulmonary TB (EPTB) is very challenging because most sites are inaccessible and paucibacillary nature of the bacteria in these sites. The need for rapid and more sensitive and specific tests for the diagnosis of EPTB in comparison to culture and histopathology is increasing. The molecular methods for the detection of M. tuberculosis gene(s) in the provided sample are now promising.

PATIENT AND METHODS: A cross-sectional descriptive study at AL-Kindy Teaching Hospital at Al-Resaffa part of Baghdad city, Iraq. Data collection has been done in three months duration (July, August, and September) 2015. A total of 74 formalin-fixed paraffin-embedded samples from suspected EPTB cases was collected, both Polymerase Chain reaction test for M. tuberculosis and histopathological examination was done for each sample.

RESULTS: A total of 74 patients (18 males, 56 females), mean age 29.72 suspected to had extrapulmonary TB underwent biopsies from different tissue types. The biopsies from the 74 patients were taken from different tissues according to the site of lesion, 49 (66.2%) biopsies were taken from lymph node, 12 biopsies (16.2%) was taken from mass in the axilla, 6 (8.1%) from abscess, 4 (5.4%) from the intestine, 3 (4.1%) from fistula. Of the 74 studied patients 57 (77%) showed positive polymerase chain reaction (PCR) and 17 (23%) showed negative PCR results. Regarding to the histopathological reports of the biopsies, there were 54 (73%) patients had positive histopathological (granuloma) result and 20 (27%) patients had negative results (nongranuloma). The sensitivity of histopathological examination of the biopsies was 91.02%, the specificity 88.2%, and the kappa was 0.748 (p = 0.00) which is mean good agreement between histopathological examination of the biopsies and the polymerase chain reaction test.

CONCLUSIONS: The sensitivity, specificity, and the positive predictive value of histopathology examination of biopsies were 91.02%, 88.2%, and 96%, respectively. The kappa was 0.748 (p = 0.00) which is mean good agreement between histopathological examination of the biopsies and the polymerase chain reaction test.