Tests
1st tests to order
no initial test
Test
Usually no tests are needed.
Result
clinical diagnosis
Investigations to avoid
serum Monospot for Epstein-Barr virus infection
Recommendations
Do not order a serum Monospot test.[29]
Rationale
The Centers for Disease Control and Prevention recommend that the Monospot test is not used. The antibodies detected by Monospot can be caused by conditions other than infectious mononucleosis and do not confirm the presence of Epstein-Barr virus infection.[29]
Tests to consider
CBC
Test
WBC count may be elevated with lymphocytosis in viral infections.
A CBC is not routinely indicated.
Result
increased WBC count, lymphocytosis
throat swab
Test
Only justified if McIsaac score of 2 to 3 or more is present.
Result
positive for Streptococcus
sputum culture
Test
May be justified in persistent infection with spread to lower respiratory tract.
A sputum culture is not routinely indicated.
Result
positive culture for bacterial pathogen
C-reactive protein (CRP)
Test
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.
Result
high CRP may indicate more serious infection
chest x-ray
Test
Indicated if signs/symptoms suggestive of lower respiratory tract spread. Not indicated as first-line investigation.
Result
no change with uncomplicated infection
sinus CT scan
Test
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.
Result
air fluid level may be present in sinusitis
viral testing
Test
Viral testing is sought only as part of research or as a tool for the early diagnosis of influenza during a pandemic. Do not routinely order broad respiratory pathogen panels in adults.[31] Do not routinely order comprehensive viral testing for children who have suspected respiratory viral illnesses as there is a lack of evidence that the results affect clinical outcomes or management.[32]
Rapid viral testing may be useful as confirmation of viral (rather than bacterial) infection, but is not routinely indicated.
Result
confirmed viral infection
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