Investigations

1st investigations to order

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May show more extensive abnormalities than physical examination would suggest.

Result

infiltrates

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Should be done for patients requiring hospitalisation. Relatively minor elevations in WBC counts (usually <13,000 x 10⁹/L [13,000/microlitre]) in patients with pneumonia suggest an atypical pathogen.

Result

may be slightly elevated; may reveal relative lymphocytosis if infection is viral

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May accompany Mycoplasma pneumoniae infections.

Result

may show anaemia

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Ordered for inpatients; elevated LFTs suggest Mycoplasma pneumoniae or Legionella pneumophila.

Result

elevated

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Low saturation indicates a more severe course of disease requiring hospitalisation.

Result

may be low (<90%)

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Elevation in urea suggests more severe disease favouring hospitalisation.

Result

70.7 mmol/L (>198 mg/dL)

Investigations to consider

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Indicated in cases of severe pneumonia and when L pneumophila infection is suspected.

Result

may be positive with Legionella angtigen

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Indicated in cases of severe pneumonia and when L pneumophila infection is suspected.

Result

may be positive with Legionella

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Either from sputum or throat swabs.

Result

may be positive with M pneumoniae or C pneumoniae

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Requires blood from early in the course of disease and a second blood specimen at least 10 days later. May be used to confirm diagnosis of many atypical pathogens and some viruses. In most cases, serology will be the main diagnostic test for Coxiella burnetii pneumonia.[35]

Result

rise in titre on convalescent serum

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Viruses can cause atypical pneumonia but may be difficult to culture and results may take days to return.

Result

may be positive with viral pneumonia

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