A precise diagnosis of viral infection needs accurate laboratory testing of clinical specimens in the presence of viral antigens, virus, or particular antibodies. The isolation of virus has largely been replaced by measurement of particular antibodies at high level of specificity and sensitivity and by sensitive nucleic acid detection assays. Here in this article, you will know about the laboratory diagnosis of viral infection.
The modern way of lab diagnosis of viral infection is considered by rapid reversal times, high throughputs tests and a close contact with clinical staff.
Most of the slower and old approaches of viral diagnosis are of little importance now such as viral inoculation in cell culture, animal inoculation and serological demo of four-fold rise in antibody titer.
Types of samples used for diagnosis of virus in laboratory:
Different sorts of samples are used for diagnosis of virus infection in laboratory. These includes
- Blood sample
- Urine sample
- Spinal fluid
- Stool sample
- Organ tissue sample
Phenomenon of laboratory diagnosis of viral infection:
- Laboratory diagnosis of viral infection is done to find out the type of infection-causing viruses. Diagnosis of viral infection is not possible through hematology tests. Viruses may have damaging effects on person’s body by altering the genetic materials of cells they infect or causing inflammation in the body. Viruses are of various types so there are different type of methods are used for different tests.
- Some of the traditional method of laboratory diagnosis of viral infections are
- direct finding in patient material of viral antigens, virions, or viral nucleic acid
- Isolating the virus in cell culture trailed by isolate’s identification
- And measurement and exposure of antibodies in serum of patient
Types of tests which are used for diagnosis of virus in laboratory:
- Antibody test
- Viral antigen detection test
- Viral RNA or DNA detection test
- Viral culture
- Antibodies are those substance which fight with specific viral disease and these antibodies are made by immune system of the body.
- The antibodies cause the virus to be destroyed by attaching themselves to those cells which are infected with virus.
- The antibody test looks for antibodies to particular infection of virus.
- This test is mainly done on a blood sample.
- The antibody can demonstrate whether the person was infected in the past or there is recent infection if antibodies were found.
Viral antigen detection test:
- Viral antigens mainly develop on the cell surface which is infected with virus.
- This done is generally done on tissue sample that might be infectious.
- Specifically tagged antibodies (with tracer or dye) that are attached with antigens of virus are mixed with the sample. Then these tagged antibodies could be visualized by special light or any other appropriate method.
- If the tagged antibody is attached to cell it indicates that the cell is infected with virus.
- Viral culture test is also used to find out the disease-causing virus.
- Here in this test, a sample of tissue or body fluid is added to specific cells that are used to grow cells.
- If there is no viral infection in the cell, it means the culture is negative.
- It there is viral infection seen in the culture cell, it means the culture is positive.
- This test took many weeks to show results.
Viral RNA or DNA detection test:
- This test is generally done on tissue cell, blood or on other body fluid e.g., spinal fluids.
- Viral DNA or RNA test looked for DNA or RNA i.e., genetic material of specific virus.
- This test illustrates the exact virus which is causing disease in person.