Investigations
1st investigations to order
rapid adenovirus immunoassay
Test
For suspected infectious conjunctivitis, rapid adenovirus immunoassay could be considered to identify adenoviral conjunctivitis in a tear fluid sample.[1][54][55][56] Sensitivity of 85% to 93%, and specificity of 94% to 99%, have been reported.[57][58]
Diagnostic tests for adenovirus are not, however, routinely used in clinical practice.[1]
Result
may be positive
Investigations to consider
conjunctival cultures
Test
Conjunctival cultures and smears for cytology and special stains (e.g., Gram, Giemsa) should be performed in all neonates with suspected infectious conjunctivitis.[1]
Viral cell culture with confirmatory immunofluorescence staining has a sensitivity of 91% and specificity of 100%.[58]
Culture may be helpful for patients with recurrent, severe, or chronic purulent conjunctivitis. Culture for routine conjunctivitis is accurate and reliable, but may not be requested because of the length of time required to obtain a result.[1]
Result
bacterial or viral isolation
special stains (Gram, Giemsa)
Test
Conjunctival cultures and smears for cytology and special stains (e.g., Gram, Giemsa) should be performed in all neonates with suspected infectious conjunctivitis.[1]
Gram staining is used in hyperacute conjunctivitis to identify gram-negative diplococci (Neisseria gonorrhoeae).[22]
Result
visualisation of bacterial organisms
polymerase chain reaction (PCR)
Test
Very sensitive; typically requiring 1-3 days for a result.
Suspected chlamydial conjunctivitis may be confirmed with laboratory testing, such as PCR or cell culture.[1][59]
Considered for chronic forms of infectious conjunctivitis to confirm the pathogen. May not be requested because of the length of time required to obtain a result.
Result
viral or bacterial DNA
ocular pH
Test
In cases of suspected chemical splash injury, ocular pH should be tested and eye irrigation continued until pH is 7.
Result
target pH is 7
allergy skin testing
Test
Allergy skin testing may be useful in more severe allergic conjunctivitis.
Allergy skin testing may identify specific allergens to target with immunosuppression.[1]
Result
identification of specific allergen(s)
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