Clinching the diagnosis--sputum and other specimens in respiratory tract infection.

Routine sputum culture in microbiology laboratories is frequently a source of dissatisfaction to microbiologists and clinicians alike. Care should be taken to ensure that the investigations requested are appropriate and that an adequate specimen is collected. Co-operation between the microbiologist and the clinician is required if the laboratory's facilities are to be properly exploited for the etiological diagnosis of respiratory tract infection. In clinical conditions such as lung abscess and atypical pneumonia sputum is not an appropriate specimen for the laboratory to work on and early consideration should be given to obtaining lower respiratory tract secretions free of oropharyngeal contamination.