Diagnosing Pneumonia without a CXR
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(1)

The diagnosis of adult pneumonia in general practice. The diagnostic value
of history, physical examination and some blood tests.
Melbye H; Straume B; Aasebo U; Brox J
Scand J Prim Health Care, 6: 2, 1988 May, 111-7

Because of lower respiratory infection that was treated with antibiotics on
the suspicion of pneumonia, 71 patients aged 15 years or more were referred
to the study by general practitioners. Using a positive chest X-ray as a
"gold standard", 15% had pneumonia. The diagnostic value of variables from
history, physical examination and blood tests was evaluated by calculating
the likelihood ratio (LR). A duration of illness less than 24 hours before
consulting the general practitioner was the variable from the history with
the highest LR, 13.5. The white blood cell count and particularly the
C-reactive protein analysis had a high diagnostic value, CRP greater than 50
mg/l had an LR of 37. In this selected material pulmonary symptoms and lung
findings were of minor value in differentiating patients with and without
pneumonia, with no LR exceeding 2.3. This can be explained to some extent by
selection bias.


(2)

Melbye H; Straume B; Aasebo U; Dale K
Diagnosis of pneumonia in adults in general practice. Relative importance of
typical symptoms and abnormal chest signs evaluated against a radiographic
reference standard.
Scand J Prim Health Care, 10: 3, 1992 Sep, 226-33

The diagnostic value of typical symptoms and abnormal chest signs for
pneumonia have been evaluated against a radiographic reference standard in
402 adult patients with respiratory tract infection in general practice.
Pneumonia was diagnosed in 20 patients by a positive chest radiograph. The
doctors diagnosed pneumonia in seven of these on the basis of history and
physical examination alone, and in addition in 22 patients with normal
radiographs. The diagnostic value of the typical symptoms cough, chest pain,
and dyspnoea, reported by the patients on a questionnaire, increased with
increasing intensity of the symptoms, and both "very annoying lateral chest
pain" and "very annoying dyspnoea" had likelihood ratios (LR) between 4 and
5. The LR of crackles was 3.7. When evaluated against the doctor's clinical
diagnosis of pneumonia as reference standard, crackles achieved an LR of
14.8, while the typical symptoms achieved lower LRs than when evaluated
against the radiographic reference standard. These discrepancies, which were
confirmed by logistic regression, indicate that crackles and other abnormal
chest findings are interpreted too frequently as features of pneumonia and
that the importance of typical symptoms is underestimated in the diagnosis
of pneumonia.