Table 1.
Comparison of the available direct methods for the detection of viruses
| Method | Assay time | Assay limit | Advantages | Disadvantages | Ref. |
|---|---|---|---|---|---|
| Virus isolation | |||||
| Conventional cell culturing | 3–10 days | 1 EID50/mL | Sensitive, accurate, broad detection range, viral isolate available | Time consuming, expertise required, not sensitive enough for all viruses | [1], [2] |
| Shell vial culturing + immunostaining | 1–3 days | NA | Faster than cell culture, detects viruses that replicate poorly in cell culture | Expertise and special equipment required, less sensitive for RSV and adenovirus, detection limited to viruses tested by pre-CPE staining | [1], [2] |
| Antigen detection | |||||
| Direct immunofluorescence Assay (DFA) | 3 h | NA | Sensitive, fast | In general, less sensitive than culturing, expertise and special equipment required | [3] |
| Immunochromatography lateral flow | <10 min | NA | Fast, specific, cheaper than PCR | Poor and variable sensitivity | [4] |
| Membrane-based enzyme immunoassays | 3 h | 1.0 ng, 103.5–105 VP | Rapid | High rate of false positives, less sensitive than DFA | [5] |
| Flow cytometry | <1 h | 2.8 × 106 VP/mL | Rapid | Less sensitive than culturing, sample needs purification | [6] |
| Nucleic acid-based detection | |||||
| Reverse transcriptase PCR (RT-PCR) | 5 h | 0.0256 HAU | Specific and sensitive | Expensive, expertise required, hardly applicable for POCT testing | [7] |
| Real-time quantitative PCR (qPCR) | 3 h | 10 copies/reaction | Rapid, specific and sensitive | Expensive, expertise required, not applicable for POCT | [8] |
| Nucleic acid sequence-based amplification (NASBA) | 6 h | 10 copies/µL | Specific and sensitive | High rate of false positives | [9], [10] |
| Reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) | 40–50 min | 0.1 pg total RNA | Simple, sensitive, rapid, visual identification, POC testing | High rate of false positives | [11], [12] |
NA, Not available; EID50, 50% egg infective dose – 1 EID50 is the amount of virus that will infect 50% of inoculated eggs; VP, Virus particles; HAU, Hemagglutination units – 1 HAU is the amount of virus needed to agglutinate an equal volume of standardized red blood cells.