Table 46.4.

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 observers) Requires high-quality reagents Obtaining good specimens requires skill, determination and persistence
Enzyme immunoassay	Relatively rapid Suitable for large numbers Can be semiautomated Detects incomplete virus particles	No feedback on specimen quality Requires high-quality reagents Automated equipment expensive Difficult to assess results at threshold of positivity
Culture	Provides more virus for further analysis Confirms presence of infective virus Generally regarded as the gold standard Only currently feasible method for some viruses (e.g. rhinoviruses and enteroviruses)	Expensive and a continuing expense Labour-intensive Some viruses difficult to isolate Mixed infections pose problems Requires high-quality reagents to identify isolates
Detection of nucleic acid by amplification (e.g. PCR, RT-PCR, NASBA, etc.)	Can be made both very sensitive and specific Can detect virus in the presence of antibody	Expensive Requires constant vigilance against cross-contamination Labour and skill intensive At present, no feedback on specimen quality