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The role of conventional diagnostic techniques in the diagnosis of respiratory tract infections

Abstract number: 1133_21

Ieven M.

In view of the increasing development of bacterial antibiotic resistance, proper and rapid diagnostic tests may result in better patient management with appropriate therapy or reduction of unnecessary antibiotic therapy. Therefore, a number of recent evidence based guidelines for the management of patients with respiratory tract infections also include guidelines on microbiological diagnosis, including both conventional and new techniques. Competition between traditional and new techniques are conditioned by: rapidity and quality of results, need for special infrastructure and trained personnel, possibility to deliver results 24/24 hours 7/7 days and cost. In pneumonia blood and pleural exsudate cultures are positive in only 4–18% and up to 40% of cases respectively. However, as they offer a highly specific diagnosis, blood cultures should be performed in hospitalised patients with CAP and thoracentesis when significant pleural fluid is present. Quantitative bacterial cultures may be important for the assessment of BAL and PSB fluid: advantages and limitations will be discussed. The most frequently submitted specimen is sputum. Criteria for good quality sputum are now universally accepted but there are still great controversies about the value of sputum Gram stain and culture. Gram strain of a valuable sputum showing a predominant morphotype correlates well with the results of boodcultures, is a rapid and low cost technique allowing a presumptive etiological diagnosis of pneumonia in many cases, allows correct interpretation of sputum culture results and therefore is recommended. Urine antigen detection is recommended for the diagnosis of L. pneumophila infections but for S. pneumoniae more studies are needed. Serological tests usually produce late results particularly for the ‘atypicals’, while the multitude of procedures for C. pneumoniae and M. pneumoniae produce divergent results. Some recent studies on the improved detection of these agents by molecular tests illustrate the often low predictive value of serology showing the limited application in the routine management of the individual patient. Based on recent studies and guidelines, indications for the use of a number of conventional diagnostic techniques in different clinical situations will be discussed. A compromise must often be found between the value of the test, feasibility turnaround time and cost.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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