Table 3.

Assays used in viral detection

Assay	Sensitivity	Specificity	Time	Cost	Expertise required	Pathogens commonly tested	Important limitations
Viral culture	+++	++++	− − −	+	− −	HSV, CMV, VZV, influenza, RSV, parainfluenza	This will routinely miss human metapneumovirus and many rhinoviruses
Rapid shell vial	+	+++	+	+	− −	HSV, CMV, VZV, influenza, RSV, parainfluenza	This will routinely miss human metapneumovirus and many rhinoviruses
Rapid antigen	–	+++	++++	+++	++++	Influenza, RSV	This assay will only detect the virus for which antigen is specifically tested. Recent literature suggests less sensitive in adults as they are in children and poor sensitivity in detecting 2009 H1N1 influenza
DFA	++	+++	+++	++	−	HSV, VZV	This assay will only detect the virus for which antigen is specifically tested
ELISA/EIA	+++	++++	+++	+	− −	Any respiratory virus	Rarely used
CMV pp65 antigenemia	++	+++	+++	+	− −	CMV	Extensive supportive literature correlation with active disease. It is limited by requiring that the patient not be neutropenic
PCR/RT-PCR	++++	++ ±	++ ±	− − −	− − −	Testing for all viruses is possible	Each virus requires molecular amplification (if not specifically tested for, it will be missed). Correlation of a positive test with active disease may be lacking (nucleic acid may remain longer than infectious or actively replicating virus). This is the current gold standard test, but laboratory contamination is always a possibility

DFA direct fluorescent antibody, ELISA/EIA enzyme-linked immunosorbent assay/enzyme immnoassay, CMV cytomegalovirus, PCR/RT-PCR polymerase chain reaction/reverse transcription–polymerase chain reaction, HSV herpes simplex virus, VZV varicella zoster virus, and RSV respiratory syncytial virus

Modified from Anderson EJ. Viral diagnostics and antiviral therapy in hematopoietic stem cell transplantation. Current pharmaceutical design 2008; 14:1997–2010. With permission from Bentham Science Publishers