elastin and Pneumonia--Bacterial

It has been inferred from previous work that 40% potassium hydroxide preparations of lower respiratory tract secretions that demonstrate elastin fibers have a 100% specificity and positive predictive value in diagnosing bacterial pneumonia in intubated, mechanically ventilated patients without the adult respiratory distress syndrome (ARDS). Our aim was to assess the specificity of 40% potassium hydroxide preparations in diagnosing bacterial pneumonia in patients with ARDS and suspected pneumonia.. Prospective, case-referral clinical study.. Referral hospital.. Of 24 patients with ARDS who were intubated and mechanically ventilated with suspected bacterial pneumonia, 22 were assessable and evaluated for this report.. Tracheo-bronchial aspirates were obtained from all patients and analyzed for elastin fibers using 40% potassium hydroxide.. Of the 22 assessable patients, ten patients did not have a complicating bacterial pneumonia. Six of these ten patients had potassium hydroxide preparations that demonstrated elastin fibers (false positives). The other four patients had preparations that did not demonstrate elastin fibers (true negatives). Specificity was 40%.. Elastin fiber preparations are not specific for diagnosing bacterial pneumonia in patients with ARDS.

Topics: Adult; Bronchi; Bronchoalveolar Lavage Fluid; Case-Control Studies; Elastin; Humans; Hydroxides; Pneumonia, Bacterial; Potassium Compounds; Predictive Value of Tests; Prospective Studies; Respiration, Artificial; Respiratory Distress Syndrome; Sensitivity and Specificity

Elastin fibre detection could be a simple and reliable marker of ventilator associated pneumonia. To confirm this, a prospective study was undertaken to evaluate the diagnostic yield of elastin fibre detection in the diagnosis of ventilator associated pneumonia.. 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 bacterial cultures of endotracheal aspirates and protected specimen brush samples were also performed. Patients were classified into three diagnostic categories: group 1, definite pneumonia (n = 25); group 2, probable pneumonia (n = 35); and group 3, controls (n = 18).. Patients 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 compared with five of the control group. Although the presence of elastin fibres had a low sensitivity (32%), it was a reasonably specific marker (72%) of pneumonia. This specificity increased to 86% and 81% respectively when only Gram negative bacilli and Pseudomonas aeruginosa pneumonia were considered. Again, calculated sensitivity was 43% and 44% when analysing cases infected by Gram negative bacilli and Ps aeruginosa, respectively. The negative predictive value of the detection of elastin fibres in pneumonia caused by Ps aeruginosa was 81%. Detection was more frequent with infection by Gram negative bacilli (14/19), particularly with Ps aeruginosa (8/14). By contrast, pneumonia due to Gram positive cocci or non-bacterial agents uncommonly resulted in positive elastin fibre preparations (4/19, 21%). When analysing patients with and without chronic obstructive pulmonary disease, the diagnostic value of elastin fibre detection did not change.. Potassium hydroxide preparation of elastin fibres is a rapid and simple specific marker of ventilator associated pneumonia and may be a useful technique to help diagnose pulmonary infections in mechanically ventilated patients, although this assessment is at present limited to patients without adult respiratory distress syndrome.

Topics: Adult; Aged; Cross Infection; Elastin; Female; Humans; Male; Middle Aged; Pneumonia, Bacterial; Prospective Studies; Pseudomonas aeruginosa; Pseudomonas Infections; Respiration, Artificial; Sensitivity and Specificity; Trachea

The evaluation of various techniques to diagnose or exclude ventilator-associated bacterial pneumonia has been a focus of much research. One such technique involves elastin fiber detection. It has been inferred from previous work that 40% potassium hydroxide preparations of respiratory secretions that demonstrate elastin fibers have a 100% specificity in diagnosing bacterial pneumonia in intubated, mechanically ventilated patients without acute diffuse lung injury. The purpose of this investigation was to ascertain if elastin fibers might be detected in respiratory secretions in acute, diffuse lung injury in the absence of pneumonia (i.e., assess specificity).. An animal model using a standardized smoke inhalation protocol to cause acute, diffuse lung injury was used.. Respiratory secretions collected from the endotracheal tubes from eight sheep that underwent the standardized smoke inhalation protocol and were examined with 40% potassium hydroxide. Histologic data were obtained from autopsy to diagnose or exclude lung injury and pneumonia.. We found six (false) positive elastin fiber preparations in the absence of histologic pneumonia. Specificity was 0.25.. We concluded that seeing these results, given a true specificity of 0.99 inferred from previous work, is highly improbable with a probability of 2.74 x 10(-7). Thus, elastin fiber analysis is likely to be highly nonspecific for diagnosing pneumonia in the setting of acute diffuse lung injury.

Topics: Acute Disease; Animals; Disease Models, Animal; Elastin; False Positive Reactions; Lung; Pneumonia, Bacterial; Respiratory Distress Syndrome; Sensitivity and Specificity; Sheep; Smoke Inhalation Injury