3-2.5 Applications
3-2.5.1 Infectious disease diagnosis, progression and response to therapy
PCR technology facilitates the detection of DNA or RNA of pathogenic organisms and, as such, helps in clinical diagnostic tests for a range of infectious agents like viruses, bacteria,protozoa etc. These PCR-based tests have numerous advantages over conventional antibody-based diagnostic methods that determine the body's immune response to a pathogen. In particular, PCR-based tests are competent to detect the presence of pathogenic agents in-advance than serologically-based methods, as patients can take weeks to develop antibodies against an contagious agent. PCR-based testshave been developed to enumerate the amount of virus in a person's blood (‘viral load') thereby allowing physicians to check their patients' disease progression and response to therapy.This has incredible potential for improving the clinical management of diseases caused by viral infection, including AIDS and hepatitis, assessment of viral load throughout and after therapy.
PCR-based diagnostics tests are available for detecting and/or quantifying a number of pathogens, including:
1. HIV-1, which causes AIDS
2. Hepatitis B and C viruses, might lead to liver cancer
3. Human Papillomavirus, might cause cervical cancer
4. Chlamydia trachomatis, might lead to infertility in women
5. Neisseria gonorrhoeae , might lead to pelvic inflammatory disease in women
6. Cytomegalovirus, might cause life threatening disease in transplant patients and other immunocompromised people, including HIV-1/AIDS patients
7. Mycobacterium tuberculosis, which in its active state causes tuberculosis and can lead to tissue damage of infected organs.
3-2.5.2 Diagnosis of genetic diseases
The use of PCR in diagnosing genetic diseases, whether due to innate genetic changes or as a result of a natural genetic mutations, is becoming more common. Abnormality can be diagnosed even prior to birth. Single-strand conformation polymorphism (SSCP), or single-strand chain polymorphism, is defined as conformational difference of single-stranded nucleotide sequences of identical length as induced by differences in the sequences under certain experimental conditions. These days, SSCP is most applicable as a diagnostic tool in molecular biology. It can be used in genotyping to detect homozygous individuals of different allelic states, as well as heterozygous individuals who inherit genetic aberrations.
3-2.5.3 Genetic counselling
Genetic counselling is done for the parents to check the account of genetic disease beforehand to make a decision on having children. This is of course governed by national laws and guidelines. Detection of genetic disease before implantation of an embryo in IVF (In vitro fertilisation) also known as pre-implantation diagnosis can also be done exploiting PCR based method. Further to diagnose inherited or a spontaneous disease, either symptomatic or asymptomatic (because of family history like Duchene muscular dystrophy) PCR based method is very useful.