Evaluation of pretreatment methods for formalin-fixed paraffin-embedded extrapulmonary tuberculosis tissue : Improvement of lab developed molecular diagnostics of Mycobacterium-complex

Sammanfattning: Tuberculosis (TB) disease is a world-wide spread disease caused by Mycobacterium tuberculosis which affects a significant percentage of the world population. The disease is often localized in the lungs, but can further develop and spread to other organs and is then called extrapulmonary TB (EPTB). The diagnosis of TB by culture is time consuming and requires specialised facilities. The use of DNA amplification is therefore an advantageous and rapid diagnostic tool. One such tool is the GeneXpert system which also can detect resistance to rifampicin (Rif) in samples. Although the system is designed to mainly analyse unprocessed sputum samples, there is a possibility to also analyse formalin-fixed paraffin-embedded (FFPE) tissue. The project's aim was to compare different pretreatment methods for processing FFPE tissue samples along with the application of Xpert MTB/Rif Ultra assay to improve EPTB case diagnosis. Tissue sections from eleven different TB negative FFPE tissue samples were used to assess three different pretreatment methods. Tissue sections from seven TB positive FFPE tissue samples were later used to validate the application of Xpert MTB/Rif Ultra assay usage. The current lab developed pretreatment method were after statistical testing and handling evaluation chosen and applied for the TB positive FFPE tissue samples. Results from the seven historical patient samples gave a 100 % positive Mtb detection result. The project's results show that the pretreatment of FFPE tissue can be applied before the Xpert MTB/Rif Ultra assay cartridges for processing on the GeneXpert instrument.