The need for chest roentgenograms in adults with acute respiratory illness. Clinical predictors.

The predictive values of several clinical variables for the presence or absence of pneumonia in adults with acute respiratory complaints were studied. Patients with congestive heart failure were excluded. Of 464 patients who received a chest roentgenogram, 129 (27.8%) had pneumonia. None of the symptoms, signs, or laboratory findings evaluated could reliably predict the presence of pneumonia. The absence of abnormal auscultatory findings on lung examination, however, excluded pneumonia with greater than 95% certainty. Among the 106 patients who presented with acute asthma, only two (1.9%) had pneumonia. Among the 33 patients with underlying organic brain syndrome, 25 (75.8%) had pneumonia. Incorporating these findings into a diagnostic strategy for ordering chest roentgenograms could have reduced the number of roentgenograms obtained by 54% and spared 72% of patients without pneumonia unnecessary radiation exposure.