Polymerase chain reaction (PCR) – the most informative, accurate and modern method for diagnosing infectious diseases, which allows you to detect the pathogen in the patient’s body, even if the number of harmful cells is calculated in units, and they have not yet had time to provoke the development of the disease. Even 25 years ago, doctors could not even dream of such opportunities, but today you can take a PCR test in any large laboratory.
PCR diagnostics has opened many other valuable prospects for people – using this technique, you can study gene mutations, establish paternity, calculate the risk of developing cancer, estimate the age and origin of archaeological artifacts, and even prove the guilt of criminals by detecting their DNA in evidence. But today we will discuss precisely the medical aspect of this discovery and tell you what diseases can be diagnosed by PCR, how to take the test and what its results mean.
PCR – what is it?
Any living creature on Earth, be it a person, an animal or a microbe, has genes – carriers of hereditary information, which are sections of DNA or RNA with a certain nucleotide sequence that is unique for each organism. DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) form long molecules consisting of two strands twisted into a spiral relative to each other, and these strands are assembled from nucleotides, like beads.
Suppose you want to see if the patient’s biological material contains DNA or RNA of an infectious agent or its fragments. But how to do this if the molecules are tiny and there are few of them? The PCR technique gives the answer: it is possible to artificially multiply harmful DNA or RNA in the laboratory in order to easily detect and identify it.
The essence of the polymerase chain reaction is to separate the strands of molecules and try to “plant” DNA or RNA fragments of pathogens to their opposite ends – if they fit, then this is the desired microbe. And an enzyme called “DNA polymerase” added to the test tube will start the synthesis of new copies of the desired sections of the molecules, they will multiply many times and become noticeable. Next, we will describe in simple terms how this amazing process occurs and why it is necessary.
In the case of real-time PCR diagnostics (Real-Time PCR), the influence of the human factor on the results of the study is minimal – the tubes are placed in a modern high-tech device and are never opened throughout all cycles, including analysis of the results, which is also carried out by a smart machine. This method has only two obvious drawbacks – high cost and limited availability, since not every laboratory is equipped with a new generation of cyclers.
[Video] Visual information – what is PCR, and how does the process work?