If you have been chosen by our friendly website, it is probably many times faced with this mysterious acronym often referred to in articles when it comes to diagnosis. It’s time once and for all to understand what lies behind these three letters, so careless throw experts in conversation with mere mortals. Well, let’s get started.
The content of the article
PCR: what is it?
PCR-diagnostics — analysis of infecties let me begin, finally, to decode the term: the acronym PCR means polymerase chain reaction. I don’t think you will immediately all became clear. That’s actually the article is being written. The value of accurate diagnosis in modern medicine is hard to overstate. Literally every year diagnosis methods become more advanced and vysokotehnologichnye. In this progressive “jet” blends with the method of PCR diagnostics, which is a reliable and valid tool laboratory research. The popularity of PCR is largely based on the breadth of its usage: it is used to identify sets of infectious diseases. In addition, it is very convenient to use as a sort of “examiner” for the doctor, checking the effectiveness of their assigned treatment.
The uniqueness of living organisms is predetermined by the genetic material each individual. Genes — small sections of DNA molecules — are a kind of “passport” of each organism, including the seedy. Yes, each species of pathogenic bacteria and viruses also have their own unique sequence and combination of nucleotides (these are the “blocks” were built DNA). To make it even clearer, the nucleotide is the structural unit of the DNA of the first order. Gene, in turn, are represented by a sequence of several nucleotides, which generally develops in a large DNA molecule.
To determine the causative agent of the disease in humans is a fence (from the word “take”) biological material: urine, blood, saliva, or swab made from the mucous membranes. If a person is sick, the biological material will contain DNA of the pathogen of the disease. But the catch is that this material is negligible for diagnosis. Here comes to the aid of the method of PCR-diagnostics. It allows you to increase the number of gene content belonging to a particular microorganism so that it can be safe to identify. That is, if it is very simplistic, the method of PCR consists of three steps:
- fence material,
- the copying of DNA in order to determine its owner,
- identification of the causative agent.
How the study PCR
As already mentioned, in the first stage, the patient “passes” of the biological material. To the already listed above, add the cerebrospinal fluid contents of the body cavities and wound discharge (the type of material used depending on the circumstances). The biomaterial is going disposable devices, and then is sterile plastic containers (or placed on a special nutrient medium) to be transported to the lab.
Upon arrival to the destination bioassay with pre-added reactant is placed in a thermostat, in which flows polymerase chain reaction, consisting of 30-50 cycles. One cycle is required from 2 to 3 minutes, therefore, you will have 2-3 hours.
Then move to the most important stage of identification. With the help of electrophoresis obtained by using PCR of DNA strands differencesbut in size. Length DNA and judge about its owner: the virus or bacteria.
Than a good PCR?
When you say “PCR”, mean “high sensitivity”, component, in different cases, from 95 to 100%. But it is characteristic of this method is not default and only in compliance with number of conditions:
- you’ll need to correctly collect and transport a bioassay in the lab;
- tools used for sampling must be sterilized and disposable;
- the analysis carried out strictly according to the method and under aseptic conditions;
- laboratory personnel must be after the medical College, and to have a high qualification.
The sensitivity of the PCR method may fluctuate slightly depending on the search object. For example, Ureaplasma is defined with a higher (99-100%) accuracy than the hepatitis C virus (97-98%), that in itself, in comparison with other diagnostic methods, is also very, very good.
Polymerase chain reaction is a very species-specific, selective method: it allows to make a conclusion about the presence in the bioassay of a specific microorganism, and not his next of kin.
Bioassay for PCR analizado many sources get to read a lot of laudatory epithets to the address of the cultural method of diagnosis (cultivation of biological material of the patient on nutrient media and subsequent identification). Not belittling the advantages of this method, considered “gold standard” for detection of most infectious diseases, it should be noted that PCR without compromising sensitivity and selectivity is clearly superior to culture method in performance analysis.
Don’t allocate PCR from a host of other diagnostic methods as the only true and right way. He gets on and combined with other methods such as enzyme immunoassay, direct immunofluorescence assay, etc., All left to the mercy of the doctor.
PCR has a very wide range of application of their “skills”. It finds application in Pediatrics, obstetrics and gynecology, venereology, urology, ophthalmology and many other areas of medicine. More specifically, you’ll read about it in the final Chapter of our story.
What can be determined by using PCR
Next you will see a list of the most common in the human population infectious agents detected by PCR-diagnostics. I’ll note that this is not the whole list of “the usual suspects”, which can be identified in this way.
- chlamydia, causing such common urogenital pathology as chlamydia;
- Mycobacterium tuberculosis, causing different tuberculosis, leprosy (leprosy);
- Legionella, which are associated with the so-called “Legionnaires ‘ disease” (not Roman, and representatives of the American Legion of veterans, after the Congress which, in 1976, was the first recorded outbreak of legionellosis);
- Salmonella causes typhoid fever and salmonellosis;
- Treponema pallidum, which, although pale, but the harm from them — the order: they are the causative agent of syphilis;
- clostridia, individual pathogenic species that cause botulism, tetanus and gas gangrene. And those Clostridium species, which are representatives of normal intestinal microflora are also capable of harm: under certain circumstances they cause diarrhea and colitis;
- cholera Vibrio. There is probably no explanation is needed;
- pathogenic species “Escherichia coli” or, speaking in Russian, Escherichia coli. They cause intestinal diseases, United under the name esherihioz occurring in the form of acute food poisoning;
- Staphylococcus aureus, whose pathogenicity is manifested the widest spectrum of diseases, ranging from acne with boils, and ending with pneumonia and meningitis;
- Rickettsia causing typhus;
- Helicobacter pylori, whose activity in the human body can cause stomach and intestinal ulcers, gastritis;
- Ureaplasma, gonococci (gonorrhea and Ureaplasma).
- retroviruses, the most well-known (one might say, infamous) of which was the human immunodeficiency virus — HIV;
- the herpes viruses;
- virus, Epstein-Barr, the main “sin” is — a infectious mononucleosis;
- cytomegalovirus, causing infection, its manifestations are similar to mononucleosis;
- hepatitis viruses;
- rubella viruses;
- HPV aka human papilloma virus;
- Rhino – and adenoviruses causing acute respiratory disease.