Functional methods of diagnosing disorders of the CFTR gene and its product

Cystic fibrosis is a hereditary disease caused by the mutation of the CFTR gene, as a consequence of the mutation of the gene is a disturbance of protein synthesis, structure and function of protein of the transmembrane conduction regulator of cystic fibrosis (CFTR), as a result of which the chlorine channels become pathologically impenetrable for chloride ions. Diagnosis of cystic fibrosis is a complex process due to the variety of mutations and phenotypes. In the article, various methods of diagnostics in historical aspect are considered. The sweat test has stood the test of time and remains in routine clinical practice the main diagnostic test that determines the function of the CFTR protein. However, false-positive and false-negative results of the sweat test are found in 12–15% of all the tests, the diagnostic complexity takes place at the borderline test results. The new methods for diagnosing cystic fibrosis and evaluating the effectiveness of targeted therapy (modulators of the protein CFTR) in the Russian Federation are following: nasal potential difference and intestinal current measurement, as well as the method of intestinal organoids. These methods are also bio-analyzers of the CFTR function. Both potential difference measurement tests were standardized and proved useful in confirming or eliminating CFTR dysfunction and take a leading place in the diagnosis of cystic fibrosis at the boundary values of the sweat samples also in the presence of rare mutations with unclear clinical significance. The review describes a test of intestinal organoids that is not diagnostic, but it can be used to understand whether a rare mutation has clinical significance for the patient and whether the patient responds to the therapeutic effects of CFTR protein modulators.

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