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More and more of us realize that prevention is easier than cure. And if it is necessary to treat it, it is much better in the early stages of the disease. But how can we be sure that we are okay? Can laboratory tests answer this question? If so, is it enough to say when you come to the laboratory: Hello, I wanted to have my blood tested?
Basic blood tests can detect diseases and find out their causes
When speaking of a blood test, many of us mean the blood count. However valuable this test is – it provides information on three groups of specialized blood cells (commonly known as “blood cells”), corresponding to, inter alia, for oxygen transfer (erythrocytes), immunity (leukocytes) and blood clotting (platelets), it is worth realizing that the modern medical laboratory offers much wider possibilities of watching what is happening in our body.
In addition to cells, blood also consists of its liquid fraction – plasma, carrying the entire mass of the substance. These include biochemical particles (such as proteins, sugars, fats), the concentration of which reflects the chemical changes constantly taking place in the body. Therefore, an abnormal blood test result may be a symptom of your disease. Hormonal abnormalities are often the cause of biochemical changes and many clinical symptoms (e.g. weight changes, growth disorders or fertility problems). Hormones such as TSH, insulin or testosterone are also transported through the bloodstream, and thus – their levels can be determined in the laboratory.
Infections – how to detect an invader?
Infections with pathogens, which include i.a. bacteria and viruses, in addition to “everyday” diseases such as colds or flu, can also cause serious diseases, such as viral hepatitis or Lyme disease. Laboratory diagnosis of infection is based on microbiological and serological tests. In the case of bacterial and fungal infections, the most commonly used are swabs from the sites of the ongoing infection – e.g. the throat, skin or genital tract. These samples are inoculated (hence the name of the test: “inoculation”), ie they are cultured for several days in order to accurately identify the invading bacteria (bacteriological test) or fungi (mycological test). At the same time, the sensitivity of a given pathogen to drugs is assessed (antibiogram and mycogram, respectively), which enables the selection of an effective therapy.
Serological markings are most commonly used in the diagnosis of viral infections, but not only. They make it possible to detect in the blood both substances produced by the body for defense – specific antibodies, and the pathogens themselves (e.g. viral antigens). These antibodies can be measured in three classes: IgA (in the case of pathogens that attack the mucous membranes, e.g. the respiratory system), IgM and IgG. Generally, IgM antibodies can be detected in the blood weeks after infection (the exact time depends on the specific pathogen) and indicate active infection. Over time, they are replaced (their level may be undetectable) by so-called antibodies. secondary immune response – IgG class, the presence of which persists for many years and indicates immunity as a result of a past infection or immunization. For the detection of antigens and antibodies, immunochemical tests are used, among which the ELISA method is the most popular. This inexpensive test is very sensitive, which means that even low levels of antibodies can be detected with it (e.g. several weeks after infection). Unfortunately, it happens that it gives the results of the so-called false positive – indicating the presence of an infection that is not really there. Therefore, it is recommended to confirm positive or doubtful results by Western Blot method, which gives unambiguous results. However, diagnostics should not be started with the Western Blot test – it does not detect such low levels of antibodies as ELISA. For some pathogens, “higher class” tests are also available – molecular tests based on the PCR technique. They enable quick detection of infection (even a few days after infection, when it is not yet revealed in the ELISA and Western Blot methods), which is of great importance for the patient and his relatives in the case of suspected infection with, for example, viruses such as HIV or HCV. The qualitative PCR test allows to determine the presence of the pathogen, and the quantitative PCR test allows to assess the dynamics of the infection.
What else can you learn from blood tests?
Autoimmune research
The development of many diseases is related to the emergence of the so-called autoantibodies, the determination of which is carried out by a laboratory diagnostic department called autoimmunology. Autoantibodies arise as a result of an error in the immune system – they recognize the body’s own structures, which, in simple terms, is associated with tissue damage and organ dysfunction. Systemic autoantibodies (found in connective tissue diseases) and organ-specific autoantibodies that recognize specific organs and even specific structures within them (e.g. gastric parietal cells characteristic of pernicious anemia or acetylcholine receptors in myasthenia gravis) can be found in the blood. Importantly, serum autoantibodies can be detected even before the clinical symptoms of the disease appear.
Genetic research
The karyotype test determines whether a person has a major genetic defect (which is synonymous with the diagnosis of a disease, e.g. Down syndrome) or is a carrier of a lesion that may cause such disease in their offspring (e.g. Robertsonian translocations). Molecular tests examining specific, small changes (mutations) in the patient’s DNA are used to detect diseases with a genetic basis (e.g. cystic fibrosis) or genetic predisposition to certain diseases (e.g. certain forms of breast cancer).
Is the treatment applied effective?
Laboratory tests are also useful in monitoring therapeutic activities. For example, the determination of the INR index (in the PT test) is necessary in the assessment of the effect of anticoagulants, and the appropriate level of glycosylated hemoglobin (HbA1C) is one of the criteria for compensating, i.e. optimal treatment, of diabetes. In cancer therapy, determination of the concentration of the so-called tumor markers. Their level is increased during the course of the disease, it should decrease after successful treatment (e.g. tumor excision), and in the event of recurrence or metastasis – increase again. However, it should be remembered that the concentration of markers may increase in inflammation conditions not associated with neoplasms, and in some patients they may be within the normal range, therefore they should not be used as the only diagnostic tool.
The effectiveness of the therapy and the lack of its side effects depend, among others, on on whether the drug reaches the proper blood levels. Currently, in routine diagnostics, it is possible to directly measure the levels of digoxin, theophylline and antiepileptic drugs.
Laboratory tests – not only blood, but also urine, feces or other body fluids can be the first sign of an ongoing disease process. They help determine its cause, which facilitates treatment, and then monitor its effectiveness. They can be performed on a medical basis or simply by coming to the laboratory, where, if necessary, we will get professional advice on the selection of tests.
Also read about the facts and myths about studying a living drop of blood