The article is devoted to problems of clinical-diagnostic value of determination of cardio-specific troponins in human biological fluids. Improvement of laboratory instrumentation and emergence of high sensitivity methods of analysis have allowed to identify troponins in urine, dialysate, and oral fluid. In the review we present actual information related to measurement of troponins in blood serum, data on testing of cardio-specific troponins in urine, dialysate, and oral fluid. Special attention is paid to determination of some cardiomarkers in oral fluid with thorough analysis of diagnostic value and effectiveness of the conducted studies.

Laboratory diagnosis plays one of the key roles in the diagnosis of many diseases, including cardiovascular diseases (CVD). The methods underlying the in vitro study of many CVD biomarkers, including cardiac troponins (cTnI and cTnT), are imperfect and are continually being improved to enhance their analytical performance, with sensitivity and specificity being the most important. Recently developed improved cTnI and cTnT detection methods, referred to as highly sensitive methods (hs-cTnI, hs-cTnT), have changed many of our ideas about the biology of cardiac troponins and opened up a number of additional diagnostic capabilities for practical healthcare. This article systematizes some relevant data on the biology of cardiac troponins as well as on methods for determining cTnI and cTnT with an analysis of the diagnostic value of their analytical characteristics (limit of blank, limit of detection, 99th percentile, coefficient of variation, and others). Data on extracardiac expression of cTnI and cTnT, mechanisms of formation and potential clinical significance of gender, age, and circadian characteristics of hs-cTnI and hs-cTnT content in serum are discussed. Considerable attention is paid to the discussion of new diagnostic capabilities of hs-cTnI, hs-cTnT, including consideration of promising possibilities for their study in biological fluids that can be obtained by non-invasive methods. Also, some possibilities of using hs-cTnI and hs-cTnT as prognostic laboratory biomarkers in healthy people (for example, to assess the risk of developing CVD) and in patients suffering from a number of pathological conditions that cause damage to cardiomyocytes are examined, and the potential mechanisms underlying the increase in hs-cTnI and hs-cTnT are discussed.

Modern laboratory methods for determining biomarkers of cardiovascular diseases are highly sensitive and can detect almost single molecules in human biological fluids, significantly speeding up and improving the diagnosis of cardiovascular diseases. However, in this case, there is a decrease in specificity and it is necessary to take into account a number of additional factors that may affect the result of the study. Recent studies have shown that circadian rhythms (CR) are among these factors. This review article is devoted to the discussion of recently discovered CR of cardiac troponins (CT). A number of articles reported that, both in healthy people and in patients with a number of chronic diseases, CT concentrations change during the day. Given that modern algorithms for diagnosing myocardial infarction (MI) are based on serial studies (0-1 h and 0-3 h) of blood serum, and the values of CT in the blood serum for the diagnosis of myocardial infarction (MI) for this period of time are only a few ng/l, the CT CR can to some extent affect the accuracy of MI diagnosis. Thus, natural physiological changes in the concentration of CT during the day can be mistakenly interpreted as diagnostically significant deviations and lead to an erroneous interpretation of laboratory test results.

Certain success has been achieved in the treatment of cancer due to the development of various effective chemotherapeutic drugs. However, an increase in their effectiveness (aggressiveness) was associated with a growth of undesirable effects on the entire human body, in particular, on the cardiovascular system. The damage to the cardiovascular system from chemotherapy in many cases is more significant than from the underlying disease. In recent years, a new direction of medicine has been formed - cardio-oncology. The major groups of cardiotoxic chemotherapeutic agents are anthracyclines, inhibitors of epidermal growth factor receptor type 2 (anti-HER2), antimetabolites, microtubule inhibitors, proteasome inhibitors, platinum-based chemotherapeutic drugs, and angiogenesis inhibitors (inhibitors of vascular endothelial growth factor). This review discusses principal pathophysiological mechanisms of the cardiotoxicity of these chemotherapeutic drugs.

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