RAPID DIAGNOSTIC METHODS IN RESPIRATORY-INFECTIONS

Rapid diagnostic methods are important in managing respiratory tract infections and in identifying epidemics at an early stage. In viral infections, diagnosis may be obtained in 1 to 5 hours by the detection of viral antigens or nucleic acids directly in the clinical specimen. During the past year, excellent reports have been published on the use of such methods for diagnosis of the influenza, parainfluenza, respiratory syncytial, rhino-, and adenoviruses. Polymerase chain reaction and sensitive immunoassays can also be used to detect other agents not normally present in the airways, ie, Mycoplasma, Chlamydia, Legionella, and Pneumocystis organisms and Mycobacterium tuberculosis. In the management of bacterial pneumonia, however, gram stain of sputum with an assessment of sputum quality and bacterial numbers is still very useful because the mere presence of the commonly causative bacteria does not imply a causative diagnosis. Detection of soluble pneumococcal polysaccharide antigen may give supplementary information, especially in patients treated with antibiotics and in those unable to produce a representative sputum specimen. Bronchoscopically obtained material is preferred when possible, both for bacterial culture and for a rapid diagnostic test.