The PCR method (polymerase chain reaction) is the "gold standard" of modern DNA diagnostics, a highly sensitive method of molecular biology. The PCR method is used in medicine, genetics, criminology and other fields. It is often and successfully used in the diagnosis of many infectious diseases.
Diagnosis of infectious diseases by PCR
The PCR test allows detecting not only the pathogen itself, but even a single fragment of foreign DNA in the material under investigation. The investigated (biological) material is: venous blood, epithelial cells and the secret of the genital tract, sperm, saliva, sputum and other biological excreta. The required biological material is determined by the alleged disease.
The PCR method in our time, of course, is a powerful diagnostic tool. Perhaps the only drawback of the study is its high price.
In the list of diseases, the presence of which can be determined by the PCR method:
- viral and bacterial pneumonia;
- tuberculosis;
- measles, rubella, parotitis;
- infectious hepatitis of all forms;
- salmonellosis, diphtheria;
- Helicobacteriosis and diseases caused by intestinal infections;
- STDs (sexually transmitted diseases): gonorrhea, chlamydia, ureaplasmosis, syphilis, AIDS, genital herpes, gardnerellez and others.
STI screening using the PCR method
Unlike traditional analyzes, the PCR technique allows detecting sexually transmitted infections (STIs) even if their symptoms are completely absent. For the collection of biological material, women are scrubbed epithelial cells of the cervical canal, men - scraping of the urethra. If necessary, the PCR method conducts a study of venous blood.
Thus, an STI test using the PCR method makes it possible to identify:
- human immunodeficiency virus (HIV);
- pale treponemus (causative agent of syphilis);
- Herpes simplex virus and cytomegalovirus;
- human papillomavirus (HPV);
- chlamydia, toxoplasm, mycoplasmas, ureaplasma and other sexual infections.
If the PCR analysis is performed correctly, the probability of false positive results is excluded. Separately, mention should be made of human papillomavirus (HPV) and the importance of the PCR method for its diagnosis. In contrast to the oncocytological smear, the PCR method can determine a specific type of HPV, in particular its oncogenic types 16 and 18, the presence of which threatens a woman with such a serious and often fatal disease as cervical cancer . Timely detection of oncogenic types of HPV by the PCR method often provides an opportunity to prevent the development of cervical cancer.
Immunoenzyme analysis (ELISA) and polymerase chain reaction (PCR) method: pluses and minuses
Which diagnostic method is better: PCR or ELISA? The correct answer to this question does not exist, since in essence the diagnosis with the help of these two studies has different purposes. And more often methods IFA and PTSR are applied in a complex.
The PCR test is necessary to determine the specific causative agent of the infection, it can be detected immediately after infection, despite the absence of a symptomatic manifestation of the disease. This method is ideal for detecting hidden and chronic bacterial and viral infections.
Unlike the PCR technique, the ELISA method is designed to detect not the causative agent of the infection, but the immune response of the organism to it, that is, to detect the presence and amount of antibodies to a particular pathogen. Depending on the type of antibodies detected (IgM, IgA, IgG), the stage of development of the infectious process can be determined.
Both methods and PCR, and ELISA have high reliability (100 and 90%, respectively). But it is important to note the fact that the analysis of ELISA in some cases gives false positive (if a person has been ill with a certain disease in the past) or false-negative (if the infection was passed relatively recently) result.