Role of PSA in cancer diagnostics
Prostate-specific antigen belongs to a broad group of tumor markers. In general, tumor markers are specific macromolecules (such as antigens, enzymes, or proteins) produced either by the tumor cells themselves or by the body in response to the development of a neoplasm.
The level of PSA in biological fluids (blood) is a crucial indicator reflecting the state of the prostate gland. Analyzing the concentration of this enzyme makes it possible to:
- determine the presence of a tumor process;
- indirectly estimate the size and stage of development of the neoplasm;
- monitor the body's response to ongoing treatment.
PSA is an organ-specific rather than a strictly tumor-specific marker. This means that it indicates pathology of a specific organ (the prostate), and its elevation can be observed not only in cancer but also in other conditions, though its diagnostic value is exceptionally high precisely in malignant growth.
Clinical significance of PSA fractions
PSA circulates in the blood in several forms. For the most accurate diagnosis of prostate cancer, physicians evaluate not only the total antigen level but also pay special attention to the ratio of its fractions:
- free;
- bound.
Analyzing this specific ratio increases screening accuracy and helps differentiate malignant neoplasms from benign changes in the organ.
Laboratory determination methods
Highly sensitive laboratory methods are used in clinical practice for the quantitative determination of PSA. The primary and most routine method for measuring the level of protein tumor markers, including PSA, is enzyme-linked immunosorbent assay (ELISA).
The essence of the ELISA method is based on the specific immunological "antigen-antibody" reaction:
- Antigens (in this case, PSA) bind to specific antibodies.
- The resulting complex is detected using a special enzymatic label.
- The label reacts with the substrate, causing a color change, which allows precise measurement of the amount of the tumor marker in the blood sample.
Class and exam questions
What are tumor markers in general?
These are specific molecules, usually proteins or enzymes, produced by a tumor or by the body in response to its growth. Their level helps determine the presence, stage of the tumor, and response to treatment.
Why is PSA called an organ-specific marker?
Because it is secreted exclusively by prostate tissues, and its elevation in the blood indicates a pathological process specifically in this organ.
Which method is most commonly used to measure PSA?
In routine practice, enzyme-linked immunosorbent assay (ELISA) is most commonly used for the quantitative determination of PSA.
What else to study on this topic
- Carcinoembryonic antigen (CEA) as a marker of colorectal cancer
- Evaluation of the p53 gene mutation and immunohistochemistry methods
- Markers of neuroblastoma: catecholamines and their metabolites
- Application of PCR in oncology (detection of KRAS, TP53, BRCA mutations)
- General questions of tumor etiology and carcinogenesis
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