TABLE 19.2.

Advantages and Disadvantages of Various Techniques of Virus Diagnosis

Technique	Advantages	Disadvantages
Immunofluorescence	Rapid, i.e. same day Allows assessment of specimen quality Sensitive and specific in experienced hands	Labour-intensive Requires experienced observer(s) Requires high-quality reagents Obtaining good specimens requires skill, determination and persistence evidence of shedding of some viruses in healthy
Enzyme immunoassay	Rapid, available in point-of-care format (~30 min) for some viruses Suitable for large numbers Can be semi-automated Detects incomplete virus particles	No feedback on specimen quality Requires high-quality reagents Automated equipment expensive Difficult to assess results at threshold of positivity Relevance of detection of viral antigens not always clear
Culture	Provides more virus for further analysis Confirms presence of replicating/infective virus Generally regarded as the gold standard	Expensive and a continuing expense Labour-intensive Not as sensitive as nucleic acid amplification, some viruses difficult to isolate or cannot be cultured Mixed infections pose problems Requires high-quality reagents to identify isolates
Detection of nucleic acid by amplification ([RT-] PCR and others)	Sensitive and specific Can detect virus in the presence of antibody Allows assessment of specimen quality Allows for multiplexed assays, random PCR-based array tests in development	Expensive Requires vigilance against false-positive results Labour- and skill-intensive Relevance of detection of viral nucleic acids not always clear