Diagnostic Techniques: Serological and Molecular Approaches

Virus laboratory diagnostics has an increasingly important role in modern patient care. Virological methods are needed to investigate the etiology of acute viral infection or the reactivation of a latent infection, as well as to follow virus load in antiviral treatments. Serological assays are also used for screening of blood products for the risk of certain chronic infections, evaluation of the immune status, and need for prophylatic treatments in connection with organ transplantations. For diagnostic purposes the following approaches can be used: demonstration of presence of infectious virus or its structural components directly from a patient's specimens or investigation of specific antibody response in serum specimes. Virus isolation is used to demonstrate infectious virus in a patient's specimens, whereas nucleic acid amplification techniques, like polymerase chain reaction (PCR), are widely used to detect virus nucleic acids. Virus antigens are investigated by antigen detection assays. Serological diagnosis is based on either the demonstration of the presence of virus-specific IgM antibodies or a significant increase in the levels of specific IgG antibodies. Immunoassays are the most commonly used serological assays. Point-of-care tests (POC tests), both for antigens and antibodies, are also becoming more and more common in diagnostic use. In order to reach the best diagnostic efficiency for each patient it is important to select the most suitable method using the right sample collected at the right time.