WBC count may be elevated with lymphocytosis in viral infections.
A CBC is not routinely indicated.
increased WBC count, lymphocytosis
Only justified if McIsaac score of 2 to 3 or more is present.
positive for Streptococcus
May be justified in persistent infection with spread to lower respiratory tract.
A sputum culture is not routinely indicated.
positive culture for bacterial pathogen
Also known as Monospot test, heterophile agglutination test, or Paul Bunnell test.
Definitive test for infectious mononucleosis.
Heterophile antibodies are present in about 80% to 90% of people with infectious mononucleosis.
Indicated in a patient presenting with extreme tiredness or persisting symptoms.
positive heterophile antibodies
CRP is an acute-phase response marker and in the correct clinical context is a surrogate marker of infection.
A CRP is not routinely indicated.
high CRP may indicate more serious infection
Indicated if signs/symptoms suggestive of lower respiratory tract spread. Not indicated as first-line investigation.
no change with uncomplicated infection
Indicated in cases of chronic maxillary or forehead pain and clinical history compatible with sinusitis.
Radiologic investigations are not routinely indicated in the common cold.
air fluid level may be present in sinusitis
Viral testing is sought only as part of research or as a tool for the early diagnosis of influenza during a pandemic.
Rapid viral testing may be useful as confirmation of viral (rather than bacterial) infection, but is not routinely indicated.
confirmed viral infection
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