T.B is mainly a bacteriological diagnosis by Ziehl-Neelsen stained smear or culture on Lowenstien Jensen Media or Middle brook). The culture on middle brook needs short duration (2-3 wks) PCR is also a recent methode . 1- Bacterial examination : If -ve for 3times, this may indicates -ve T.B infection ? • Mycobacteria is recognized by their surface lipids which makes them acid fast in the laboratory examination. • Isolation of organism from 2-Radiological picture: (usually gives apical lesion) * Cavity * Fibrosis * Consolidation * Effusion * Collapse * Miliary shadow3-Tuberculin skin test: • It is used widely to screen certain high risk populations, particularly those who have been exposed to an infectious patients. • The test involves an intradermal injection of the purified protein derivative (PPD) of the bacilli. • After 48-72 hours the injection site is examined for visible and palpable induration. • Because of a possible cross reaction after exposure to other mycobacteria a single tuberculin test to determine sensitization to mycobacterium tuberculosis is considered positive only if the diameter of the induration at the skin test site measures : Read more at :Tuberculosis diagnostic investigations and Tuberculin test
