Molecular diagnosis corresponds to a set of molecular techniques that aim to identify changes in DNA that could be indicative of genetic diseases or cancer, for example. In addition, molecular techniques are being widely used for the identification and confirmation of infectious diseases, as they represent a faster and more accurate diagnostic method.
Molecular diagnosis is expensive and, therefore, is not requested very often by doctors, however, it gives accurate results with regard to the presence of the change, the way it can interfere with the functioning of the organism and the patient's response to treatment.
What is it for
Molecular diagnosis can be performed with several objectives, the main ones being:
- Identification of leukemia- related mutations, such as the identification of BCR-ABL translocation, which is characteristic of Chronic Myeloid Leukemia (CML); Characteristic mutations of hematological diseases, such as hereditary hemochromatosis, polycythemia vera, essential thrombocythemia and thrombophilia, for example Molecular changes that indicate the occurrence of cancer, such as colorectal, lung, breast and brain cancer, for example; Diagnosis of infectious diseases, such as hepatitis, urethritis, toxoplasmosis, leishmaniasis, etc., in addition to the identification of the HPV virus.
Molecular diagnosis, despite being considered expensive when compared to other diagnostic techniques, is more accurate, as it is able to inform the change related to a certain disease and the degree of influence of this change in the body, thus helping the person's treatment.
In addition to being used for the diagnosis of various diseases, molecular techniques are also used to assess the response to treatment, especially in people with cancer, being one of the most effective methods to indicate disease progression and relapse.
How is done
The molecular diagnosis can be performed with any sample, being requested by the doctor the one that can best provide information about the patient's condition, which can be urine, saliva or, in most cases, blood. There is no need for fasting or any other preparation for the exam.
The sample is collected and sent to the laboratory together with the doctor's guidance informing the exam or type of research that should be done. The molecular technique performed depends on the requested exam and involves a series of precise procedures that aim to identify the presence or absence of the alteration requested by the doctor.
Usually only a small amount of sample sent is used, the rest being stored so that, if necessary, the exam is repeated.
See what are the main molecular techniques
PCR
PCR, short for Polymerase Chain Reaction or Polymerase Chain Reaction , is a molecular technique that consists of the amplification of a fragment of genetic material, either DNA or RNA, with the objective of identifying mutations and, thus, helping in the diagnosis of diseases.
This technique is made from the extraction and purification of the genetic material, which is then placed in a mix in which one of the components is a restriction enzyme that varies according to the requested examination and whose function is to cut the material into fragments so that the possible genetic alteration can be identified. The mix is placed in a thermocycler, which is a device that acts through the temperature variation indicated by the professional according to the exam and, thus, allows the amplification of the genetic fragment. In the case of conventional PCR, after amplification, the PCR product is subjected to electrophoresis, which is a molecular technique based on the weight and size of the fragments, that is, according to these characteristics, a band pattern is generated, whose analysis is made based on the positive control band, that is, the band known to correspond to the genetic alteration.
Real-time PCR, also called qPCR, is a type of quantitative PCR, that is, in addition to identifying the genetic alteration, it is able to provide information on gene expression, that is, how much the altered gene is being expressed in the organism., thus, it can be used to aid diagnosis and monitor treatment. Real-time PCR does not require electrophoresis, the entire process of amplifying and analyzing genetic material is done by a device and the result is interpreted by a trained health professional.
Sequencing
Sequencing is a molecular technique that consists of determining the sequence of DNA nucleotides, which are the forming units of genetic material. Sequencing occurs from a reaction similar to PCR, however, in the amplification mix, modified nucleotides are added by the addition of fluorochromes, which as the material is amplified, the modified nucleotides are incorporated into the DNA and generate several fragments, which correspond to the sequencing product.
The reaction product is placed in a device called DNA sequencer, in which, as the fragments are reached by the equipment's laser, the fluorochromes are excited, emitting fluorescence, which is indicated by the equipment by means of peaks, with each peak corresponding to a nucleotide. At the end of the reaction, the equipment will inform the DNA sequence, thus being able to assist the doctor in the diagnosis of genetic diseases.
