USE OF ELASTIN FIBER DETECTION IN THE DIAGNOSIS OF VENTILATOR-ASSOCIATED PNEUMONIA

Background - Elastin fibre detection could be a simple and reliable ma rker of ventilator associated pneumonia. To confirm this, a prospectiv e study was undertaken to evaluate the diagnostic yield of elastin fib re detection in the diagnosis of ventilator associated pneumonia. Meth ods - Seventy eight mechanically ventilated patients were evaluated by examining endotracheal aspirates for the presence of elastin fibres. All patients were previously treated with antibiotics. Quantitative ba cterial cultures of endotracheal aspirates and protected specimen brus h samples were also performed. Patients were classified into three dia gnostic categories: group 1, definite pneumonia (n = 25); group 2, pro bable pneumonia (n = 35); and group 3, controls (n = 18). Results - Pa tients with definite and probable pneumonia were grouped together. The presence of elastin fibres in endotracheal aspirate samples was more frequent in groups 1 and 2, being found in 19 of the 60 patients compa red with five of the control group. Although the presence of elastin f ibres had a low sensitivity (32%), it was a reasonably specific marker (72%) of pneumonia. This specificity increased to 86% and 81% respect ively when only Gram negative bacilli and Pseudomonas aeruginosa pneum onia were considered. Again, calculated sensitivity was 43% and 44% wh en analysing cases infected by Gram negative bacilli and Ps aeruginosa , respectively. The negative predictive value of the detection of elas tin fibres in pneumonia caused by Ps aeruginosa was 81%. Detection was more frequent with infection by Gram negative bacilli (14/19), partic ularly with Ps aeruginosa (8/14). By contrast, pneumonia due to Gram p ositive cocci or non-bacterial agents uncommonly resulted in positive elastin fibre preparations (4/19, 21%). When analysing patients with a nd without chronic obstructive pulmonary disease, the diagnostic value of elastin fibre detection did not change. Conclusions - Potassium hy droxide preparation of elastin fibres is a rapid and simple specific m arker of ventilator associated pneumonia and may be a useful technique to help diagnose pulmonary infections in mechanically ventilated pati ents, although this assessment is at present limited to patients witho ut adult respiratory distress syndrome.