Clinical Signs Accurately Identify Pneumonia, Study Suggests

Jennifer Garcia

November 29, 2017

Four clinical variables — the presence of fever, elevated pulse rate, crackles on auscultation, and low oxygen saturation — can help identify patients with pneumonia in the primary care setting, according to new data.

"[T]he four variables identified by this analysis are easily measured clinical signs," write Michael Moore, BM BS, MRCP, FRCGP, from the University of Southampton, Aldermoor Health Centre, United Kingdom, and colleagues.

"If antibiotic prescribing was restricted to people who had one or more of these signs, it could substantially reduce antibiotic prescribing for this condition," the authors write in an article published online November 22 in the European Respiratory Journal.

For the prospective cohort study, the researchers evaluated 28,883 patients between 2009 and 2013 who presented to their primary care provider with symptoms of acute cough attributed to a lower respiratory tract infection

Among the 720 patients radiographed within the first week after their initial consultation, 16% (115/720) were diagnosed as having definite or probable pneumonia.

The researchers noted specific independent predictors of radiograph-confirmed pneumonia among this cohort, including temperature 37.8°C or higher (risk ratio [RR], 2.65; 95% confidence interval [CI], 1.46 - 4.81), pulse rate 100/minute or higher (RR, 1.90; 95% CI, 1.12 - 3.24), crackles on auscultation (RR, 1.82; 95% CI, 1.12 - 2.97), and oxygen saturation below 95% (RR, 1.73; 95% CI, 0.98 - 3.06).

Overall, 86.1% (99/115) of patients with pneumonia exhibited at least one of these clinical signs. In contrast, other factors, including presenting symptoms, age, sex, smoking history, and past medical history, provided no predictive information for a pneumonia diagnosis.

The authors note that previous studies have found fever, crackles, and elevated pulse rate to be predictors for the presence of pneumonia. However, unlike the current best diagnostic model, the presence of a runny nose was not found to be significant in the present study. In contrast, the addition of pulse oximetry has demonstrated clinical utility in previous retrospective studies in the primary care setting.

The researchers acknowledge limitations to the study, primarily that thoracic radiographs were only obtained in a small sample of the full cohort and that those patients selected for radiography were more ill and at higher risk for pneumonia. This may have resulted in fewer reported cases of radiograph-confirmed pneumonia in the cohort as a whole, and as well as overemphasis of the importance of the four clinical signs as positive predictors of pneumonia.

Given this limitation, the study authors caution that, although pulse oximetry may have a role in the diagnosis of pneumonia, further studies that include comprehensive assessment, including thoracic radiographs, will be required.

Funding for this study was provided through a grant from the National Institute for Health Research. The authors have disclosed no relevant financial relationships.

Eur Respir J. Published online November 22, 2017. Full text

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