Confirmatory test for tuberculosis is: September 2006

Ans. B: AFB The diagnosis of tuberculosis requires detection of acid-fast bacilli in sputum the Ziehl-Neelsen method Mycobacteria retains the primary stain even after exposure to decolorising acid-alcohol, hence the term 'acid-fast'. A counter-stain is employed to highlight the stained organisms for easier recognition. There are several methods of determining the acid-fast nature of mycobacteria. In the carbolfuchsin (Ziehl-Neelsen) procedure, acid-fast organisms appear red against a blue background, while in the fluorochrome procedures (auramine-O, auramine-rhodamine), the acid-fast organisms appear as fluorescent rods, yellow to orange (the colour may vary with the filter system used) against a paler yellow or orange background. Tuberculin testing may be used as an aid in diagnosing active infection in infants and young children,to measure prevalence of infection in an area, to select susceptible or as an indication of successful vaccination.