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Algorithm for determining tumor markers
Last reviewed: 23.04.2024
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Specificity of tumor markers - the percentage of healthy individuals and patients with benign tumors, in which the test gives a negative result.
The sensitivity of the oncomarker is the percentage of results that are truly positive in the presence of this tumor.
Threshold concentration (the point of separation) is the upper limit of oncomarker concentration in healthy individuals and in patients with non-malignant neoplasms.
The objectives of the definition of oncomarkers in clinical practice
- An additional method for diagnosing cancer in combination with other methods of research.
- Management of oncological patients - monitoring of therapy and control of the course of the disease, identification of tumor remains, multiple tumors and metastases (concentration of oncomarker may be increased after treatment due to tumor disintegration, therefore, the study should be conducted 14-21 days after the start of treatment).
- Early detection of tumor and metastases (screening in risk groups - PSA and AFP);
- Determination of disease prognosis.
Scheme of appointment of oncomarker research
- Determine the level of oncomarker before treatment and further investigate those oncomarkers that have been elevated.
- After the course of treatment (operation), examine after 2-10 days (corresponding to the half-life of the marker) in order to establish the baseline level for further monitoring.
- To assess the effectiveness of treatment (operation) to conduct a study after 1 month.
- Further study of the level of the oncomarker in the blood should be carried out once a month during the first year after treatment, once in 2 months during the 2nd year after treatment, once every 3 months for 3-5 years (WHO recommendations).
- Conduct an oncomarker study before any treatment change.
- To determine the level of oncomarker in case of suspected relapse and metastasis.
- Determine the level of oncomarker after 3-4 weeks after the first detection of its increase.
Factors affecting in vitro on the concentration of oncomarkers in the blood
- Conditions of storage of blood serum (should be stored in the cold).
- Time between sampling and centrifugation (no more than 1 hour).
- Hemolysed blood serum (increased concentration of HCE).
- Contamination of the sample (increased concentration of CEA and CA 19-9).
- Taking medications (increase the concentration of PSA ascorbic acid, estradiol, ions of 2- and 3-valent metals, guanidine analogs, nitrates, etc.).
[8], [9], [10], [11], [12], [13]
Factors affecting in vivo on the concentration of oncomarkers in the blood
- Produce tumor of oncomarker.
- Isolation into the blood of oncomarker.
- Tumor weight.
- Blood supply to the tumor.
- Daily variations (it is necessary to take blood for the study at the same time).
- The position of the body at the time of taking the blood.
- The influence of instrumental studies (X-rays increase the concentration of HCE, colonoscopy, digital rectal examination - PSA, biopsy - AFP).
- Catabolism of the oncomarker (functioning of the kidneys, liver, cholestasis).
- Alcoholism, smoking.