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Elastin fibers and the diagnosis of bacterial pneumonia in the adult respiratory distress syndrome.

OBJECTIVE
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.


DESIGN
Prospective, case-referral clinical study.


SETTING
Referral hospital.


PATIENTS
Of 24 patients with ARDS who were intubated and mechanically ventilated with suspected bacterial pneumonia, 22 were assessable and evaluated for this report.


INTERVENTIONS
Tracheo-bronchial aspirates were obtained from all patients and analyzed for elastin fibers using 40% potassium hydroxide.


MEASUREMENTS AND MAIN RESULTS
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%.


CONCLUSION
Elastin fiber preparations are not specific for diagnosing bacterial pneumonia in patients with ARDS.