**5. Conclusions**

In modern medicine we strive for an individual approach to each patient. This strategy is mainly based on clinical phenotyping, where biomarkers play an important role. Additionally, in childhood diseases, especially in asthma, problems with diagnostics and assessment of treatment efficacy often occur due to a lack of cooperation with young patient. Thus, many molecules, metabolites, and proteins remain the subject of research to find a simple, useful biomarker that may solve the abovementioned problems. The potential relevance of molecules, such as (in blood) eosinophil cationic protein, periostin, lipoxins, chitinases, YKL-40, (in exhaled breath) fractional exhaled nitric oxide, volatile organic compounds, evaluation of exhaled breath temperature, (in urine) bromotyrosine, metabolites of eicosanoids, eosinophil-derived neurotoxin in diagnostics and management of asthma were evaluated. Unfortunately, these biomarkers presented several limitations, e.g., particles detected in the urine do not directly reflect the inflammatory process in the respiratory tract and the concentration of some molecules changes during the growth of children or in the course of other diseases [44–46]. These facts make them useless in clinical practice. Therefore, understanding the importance of new, promising biomarkers

(miRNAs) and their role in metabolic pathways in childhood asthma seems to be crucial. Based on the considerations presented in this manuscript, it can be seen that miRNAs, in combination with disease symptoms, lung function tests, and allergy tests, seem to be a useful tool in the construction of predictive models, allowing for the identification of high-risk groups for the adverse course of the disease and increasing the probability of making an accurate diagnosis in an ambiguous case. In order for miRNAs to be introduced into common clinical practice, the methods of their detection should be characterized by high sensitivity and specificity. Based on many studies, it has been shown that they indeed have such potential; however, a lack of data prevents their successful implementation in clinical practice. Therefore, there is a need to conduct new analyses and search for solutions using miRNA molecules in the population of pediatric patients diagnosed or suspected of having bronchial asthma.

**Author Contributions:** N.K.-G. and B.S. conceived of the review and drafted the manuscript. The review was performed under the supervision of B.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** No new data were created or analyzed in this study. Data sharing is not applicable to this article.

**Conflicts of Interest:** The authors declare no conflict of interest.
