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What is A man presents with fever, wt loss and cough; Mantoux reads an induration of 17 x 19 mm: Sputum cytology is negative for AFB. Most likely diagnosis is: and explain in detail?
Answer is A (Pulmonary tuberculosis): All features mentioned in this question are in our of pulmonary tuberculosis and the only feature that troubles is a 'negative sputum cytology'. A negative sputum cytology however does not rule out pulmonary tuberculosis. 'A negative sputum cytology does not rule out pulmonary tuberculosis'- CMDT `There is a definite set for patients of 'suspected TB with negative sputum smears'. These patients are usually investigated by bronchoscopy as the next diagnostic step. Bronchial washings and transbronchial lung biopsies are specially helpful and increase the diagnostic yield'. - CMDT Definitive diagnosis of TB : Does not depend on sputum cytology but, it depends on recovery of Mycobacterium TB in cultures or identification of organism by DNA probe. Remember: "demonstration of acid fast bacilli on sputum smears does not confirm a diagnosis of TB". Since saphrophytic and non tuberculous mycobacteria make colonize the airways or cause pulmonary disease. It is sputum culture with demonstration of M. TB that is diagnostic.