What is a screening test? Nine Essential Medical Screening Tests for Men

09.03.2020 -

SCREENING- in 1951, the US Commission on chronic diseases defined screening as: “The presumptive identification of an unrecognized disease or defect by means of tests, examinations, or other easily administered procedures.”
Screening tests can distinguish between apparently healthy people those who are likely to have the disease and those who are likely not to have it. The screening test is not intended to be diagnostic. Individuals with positive or suspicious results should be referred to their physicians for diagnosis and treatment. necessary treatment" The initiative to conduct screening usually comes from the researcher, person or organization that provides medical care, and not from the patient with complaints. Typically screening is aimed at chronic diseases and to identify the disease for which health care It doesn't turn out yet. Screening allows you to identify risk factors, genetic predispositions and harbingers or early manifestations diseases. Exist different types medical screening, each of which has its own focus.

Types of screening

Mass screening(Mass S.) simply means screening the entire population.
Complex or multidimensional screening(Multiple or multiphasic S.) involves the use of various screening tests at the same time.
Preventive screening(Prescriptive S.) is aimed at the early detection of diseases in apparently healthy people, the control of which may be more successful if detected at an early stage. Example: Mammography to detect breast cancer. Characteristics of a screening test include accuracy, estimated number of cases detected, accuracy, precision, sensitivity, specificity, and validity. (See also: detectable preclinical period, measurements.)
Selective screening- carried out in the absence of symptoms, but in the presence of one or more risk factors for developing the disease being sought, for example, indications of diseases in immediate relatives, lifestyle characteristics, or the subject’s belonging to a population with a high prevalence of the corresponding disease
Genetic screening(GENETIC SCREENING) - the use of molecular biology methods to identify mutations that are present in humans and increase the risk of developing a disease, for example, the BRCA1 and BRCA2 genes, which significantly increase the risk of developing breast and ovarian cancer in women. Genetic screening may raise ethical issues, such as notifying people that they are at increased risk for a disease, effective treatment which does not exist. Problems may also arise if the diagnostic result could lead to problems with employment and insurance.
Systematic (sample-free) screening– carried out to all individuals in a certain population, for example, ultrasound screening of chromosomal pathology, which is carried out in the first trimester of pregnancy. The population for this screening is all pregnant women without exception.
Selective screening– carried out among persons exposed to certain risk factors that can cause a particular disease. An example of such screening is the study medical workers on the incidence of hepatitis B and C, HIV, syphilis, because representatives of these professions come into contact with biological fluids of potentially sick people and, accordingly, have an increased risk of contracting these infectious diseases.

Terms and concepts characterizing screening

Screening level(SCREENING LEVEL) - the limit of the “norm” or the separation point beyond which the screening test is considered positive.
Sensitivity and Specificity
Prognostic value of a diagnostic test
Likelihood ratio
False positive results
False Negatives

Screening criteria

Below are the screening criteria proposed by the UK NATIONAL SCREENING COMMITTEE:
Screenable disease or condition

The disease or condition being screened has a significant impact on the patient's health;
The etiology and pathogenesis of the disease must be carefully studied, risk factors for the development of the disease and its signs must be known, which can be identified in the latent or early stages of its development;
All effective measures aimed at preventing the development of the disease must be applied;
Possible ethical and psychological consequences screening for individuals who are carriers of a gene mutation when screening for gene diseases with a recessive type of inheritance.

Screening test

Must be simple to implement, safe for the patient’s health, accurate and reliable;
Should be known normal distribution the values obtained as a result of the test in the population being examined, and an acceptable threshold level of test values must be established at which the screening result will be considered positive;
the test must be acceptable to the population being tested;
Screening for gene-related diseases should be carried out only for those diseases for which it is possible to diagnose all possible gene mutations that cause the disease. If it is not possible to diagnose all gene mutations, screening for a given gene disease should not be performed.

Treatment

If the disease is diagnosed at an early stage, there must be an effective treatment.
Effectiveness on disease outcomes when diagnosed and treated early must be demonstrated in clinical trials
Before introducing a screening program into clinical practice, a clear organization of the actions of all health care institutions involved in screening and treatment of this disease is necessary.

Screening program
The developed screening program must meet a number of requirements:

The effectiveness of the screening program should be confirmed in the framework of RCTs. Main criteria: reduction in morbidity and mortality from the disease being screened.
Evidence of the accuracy of the screening test to detect the disease under study.
Proposed screening studies must be clinically acceptable and ethical
The benefits of screening must outweigh the potential physical and psychological harm that the patient may experience as a result of participating in the screening program.
Economic feasibility: the cost of screening should not exceed the costs of diagnosing and treating the disease if it is detected at a later date.
Constant quality control of the current program
Before implementing a screening program, you should ensure that there is sufficient equipment and specialists to implement it.
Patients should be informed about the possible results of the screening. Information must be conveyed in a language that the patient understands.
Screening for the detection of gene diseases with a recessive type of inheritance should be acceptable for carriers of the recessive gene and its relatives.

Screening tests are already performed on newborns. They can detect hypothyroidism, cystic fibrosis and many metabolic diseases, the early detection of which helps to avoid complications. In adults, screening is primarily aimed at quickly detecting precancerous lesions.

Screening tests are diagnostic tests that are performed on people who are healthy but at risk for certain diseases, such as cancer. They are held in different age groups, which allows you to quickly identify and prevent the development of certain diseases. The youngest group for screening tests is newborns on the first day of life.

What are screening tests?

The screening study aims to identify people who need closer monitoring, broader diagnosis and the ability to intervene quickly in people at increased risk. There are many examples of screening tests. They are characterized by special specificity and sensitivity. High sensitivity avoids false negatives, while the specificity of the test prevents false positives.

Cytology can be a screening test. This is performed in women to detect early pathological changes in the cervix.
Colonoscopy is a good screening test for colorectal cancer in men over 40 years of age.
Screening tests for newborns are already performed in the first hours of life. They help prevent up to 27 diseases.

Screening tests for newborns

Screening tests for newborns are performed from a few drops of blood obtained after pricking the newborn's heel and placing it on paper (previously detailed with the personal data of the mother and child). Regardless of whether the newborn is completely healthy or not, regardless of whether he has a family history, screening is carried out in any case. They make it possible to detect a disease before it manifests itself, and treatment prevents the development of childhood disability.

Newborn screening tests can detect hypothyroidism, cystic fibrosis, phenylketonuria, and many metabolic disorders. One of the most common diseases among the European population, identified during screening tests in newborns, is cystic fibrosis. Newborn screening involves determining the level of immunoreactive trypsin in a dried blood spot. If levels are abnormal, a DNA test is performed to look for a mutation in the CFTR gene. The final diagnosis is based on clinical assessment of newborns, genetic tests, as well as determining the concentration of chlorides in sweat. It happens that the result is ambiguous. Such children should be under the supervision of a doctor, and a second examination should be carried out in the second half of the year of life.

Another screening test for newborns and newborns is speech therapy. It includes assessment of craniofacial and oral anatomy. The speech therapist's job is to check whether the baby has any abnormalities affecting respiratory, nutritional, and speech functions that impede speech development.

Types of Screening Tests

Each screening test is performed differently. Part can be performed during regular blood collection.

Cytological tests to detect precancerous lesions and cervical cancer are performed by removing the epithelium from the cervix. Mammography, on the other hand, is an examination of the breast using X-rays. It is held for early diagnosis breast cancer in women over 40 years of age.

Colonoscopy is a screening test that should be performed especially in men over 40 years of age. It consists of inserting a special endoscope through the rectum into the colon to evaluate the intestinal mucosa and possible removal samples for histopathological examination. Colonoscopy is performed for early detection colon cancer, which unfortunately continues to be associated with high morbidity and mortality. Because of the asymptomatic onset and late detection of the disease, screening for people at increased risk is important.

Other screening tests are, for example, standard blood tests such as morphology, total cholesterol and its individual fractions - LDL or HDL, fasting glucose measurement. We can also mention many other tests that are performed on almost everyone healthy person. All this makes it possible to quickly detect conditions that predispose to atherosclerosis, diabetes and hypertension.

Not unusual. In accordance with the FIGO Recommendations (2015) 1, if the calculated risk of having a child with a chromosomal abnormality is 1:100 or higher, the patient must be offered clarifying tests. Every time we get “bad” results, we worry along with the patient, but we try to explain that it is too early to cry. Clarifying tests most often make it possible to reliably prove that the baby is healthy.

- All the girls were crying there, I was the only one who was sure that everything would be okay! - the pregnant woman tells me, proudly showing a piece of paper with the result 46XY. We will have a great one healthy boy without chromosomal pathology.

Yes, the likelihood that the child is completely healthy is very high. But if the fetus does have genetic abnormalities, you need to know about it in advance. Consultation in such cases is carried out by specialists in medical genetics, who can talk in detail about the results of clarifying testing and help parents decide whether to continue or terminate the pregnancy.

In fact, there are only two clarifying tests - invasive and non-invasive. An invasive test is an intervention in the world around the fetus to obtain cellular material. Non-invasive - a study that is carried out on the mother's blood. Of course, donating blood from a vein after the 10th week of pregnancy is not at all scary, but it is very expensive and is not covered by the compulsory medical insurance fund. Both methods have their limitations, so it is worth considering them in more detail.

Invasive tests

Invasive tests are performed by highly qualified specialists. The purpose of the tests is to obtain fetal cells to study its chromosome set. At 10–13 weeks it is carried out chorionic villus biopsy. A special instrument is inserted through the cervix to pinch off small fragments of the placenta.

If the time for chorionic villus biopsy is missed, a amniocentesis- under ultrasound control, a puncture is made with a thin needle and not collected a large number of amniotic fluid.

Both procedures have their own risks and a 1-2% chance of miscarriage. That is why invasive tests are recommended only in cases where the likelihood of having a child with a chromosomal disorder is higher than 1–2%.

Cells obtained through invasive procedures can be examined different ways:

karyotyping- the study is carried out within 2 weeks, the fetal chromosomes are arranged in a special order and it is ensured that there are no extra or damaged ones in the set;
FISH method - quick way exclude the most common anomalies in the 13th, 18th, 21st pair and anomalies of the sex chromosomes X and Y. If abnormalities are found, karyotyping is required;
advanced molecular genetic analysis, which can detect microdeletions - small chromosome breaks that lead to serious illnesses;
specific DNA tests for specific diseases. For example, if healthy parents are carriers of the cystic fibrosis gene, they can each pass on a “diseased” gene to their child, and the child will suffer from a serious illness.

NIPT - non-invasive prenatal testing

This is absolutely new method, which has been gradually entering clinical practice since 2011. Starting from the 9th–10th week of pregnancy, placental cells (trophoblasts) are isolated from the mother’s blood and their DNA is examined. This turned out to be enough to very early pregnancy (before the standard first screening) to accurately diagnose chromosomal pathology of the fetus.

The new method demonstrates excellent efficiency. According to researchers, out of 265 women with “poor” results of standard screening, only 9 patients will actually have a chromosomal pathology of the fetus identified 2. If pathology is detected using NIPT, invasive methods will confirm the disease in 9 out of 10 fetuses 3 .

NIPT is a fairly expensive study. Highly accurate determination of the sex of a child is a very small free bonus of the method. Of course, the more parameters to be studied, the more expensive analysis. A standard NIPT panel with 99% accuracy allows you to exclude Down syndrome, Edwards syndrome, Patau syndrome and sex chromosome abnormalities (this large group diseases when instead of two sex chromosomes one, three or even four are found).

The most expensive option is an extended study with microdeletions (small chromosome breaks), which makes it possible to exclude/confirm 22q11.2 deletion (DiGeorge syndrome), 1p36 deletion (Angelman syndrome, Prader-Willi syndrome, cat cry syndrome).

For example, 22q11.2 deletion of the fetus in young mothers is detected more often than Down syndrome 4, and this pathology may not be immediately noticed even in newborns, but it is characterized by birth defects heart, structural anomalies of the palate, developmental delay, schizophrenia at a young age.

You can find a huge number of indications for this test on the Internet. This includes the mother’s age 35+, habitual miscarriage, and cases of such children being born in the family. In fact, the only indication for NIPT is woman's desire.

FIGO in 2015 proposed using the following diagnostic algorithm:

at a risk of 1:100 and above, carry out immediately invasive diagnostics, or NIPT first, then invasive diagnostics for those with an abnormal result;
at a risk from 1:101 to 1:2500, NIPT is recommended;
if the risk is less than 1:2500, in-depth prenatal screening is not indicated.

It is much more important to understand in which cases the use of NIPT is impossible or inappropriate:

history of blood transfusion;
transfer bone marrow in the anamnesis;
oncological diseases mothers;
multiple pregnancy (three or more fetuses);
twins in which one of the fetuses froze;
donor egg/Surrogacy;
the presence of ultrasound markers of chromosomal pathologies (in this case, NIPT is no longer needed).

In this case, it is very difficult to separate whose DNA is whose (the mother’s, one, or second, or third fetus, blood or tissue donor), so the results are uninformative.

Non-invasive tests have different brand names (Panorama, Prenetix, Harmony, Veracity) and differ slightly in the technique of execution. Each company carefully cherishes its “idea” and believes that its NIPT is much better than others.

What should you consider?

If the first screening reveals a high risk of chromosomal abnormalities, it is important to understand that the risk is not a diagnosis. But if a woman is categorically against having a child with a chromosomal abnormality (it is important to understand that at the current stage of development of medicine such diseases are incurable), an invasive test is mandatory. Termination of pregnancy after the 12th week is possible only by decision medical commission with serious arguments in hand.

If a woman decides to carry the pregnancy to term in any case, she has the right to refuse further diagnostic procedures. At the same time, more certain information will help parents prepare for the birth of a “syndromic” child: find support groups on social networks, talk with parents raising such children, draw up a medical care plan in advance.

When it comes to choosing between invasive techniques and NIPT, it is important to understand that invasive test materials can be examined in different ways - and detect all sorts of diseases. And the NIPT technique answers only those questions formulated by the doctor. That is why the “last word” still remains with invasive diagnostics, although false positive results occur with any type of testing.

Parents also have the right to completely refuse screening or any clarifying tests. In this case, it is sufficient to sign an informed voluntary refusal to intervene. However, if a woman changes her mind and still wants to undergo testing, some of them (those that are carried out strictly during certain periods of pregnancy) will no longer be possible.

Oksana Bogdashevskaya

Photo istockphoto.com

1. Best practice in maternal-fetal medicine. Figo Working Group On Best Practice in Maternal-Fetal Medicine // Int. J. Gynaecol. Obstet. 2015. Vol. 128. P. 80–82.
2. Norton M.E., Wapner R.J. Cell-free DNA analysis for noninvasive examination of trisomy // N Engl J Med. 2015. Dec 24; 373(26):2582.
3. Dar P., Curnow K.J., Gross S.J. Clinical experience and follow-up with large scale single-nucleotide polymorphism-based noninvasive prenatal aneuploidy testing // Am J Obstet Gynecol. 2014 Nov; 211(5):527.
4. Combined prevalence using higher end of published ranges from Gross et al. // Prenatal Diagnosis. 2011; 39, 259-266.

Diagnosis differs by type of disease: infectious, nervous, cardiovascular, oncological, lung diseases. liver and other organs, childhood diseases, etc. Diagnosis of diseases may include a specific research method or a complex of different methods.

Depending on the patient’s complaints and clinical manifestations of the disease, he is prescribed a number of examinations:

Blood and urine tests;
Ultrasound examination of internal organs;
X-ray research methods;
Endoscopic research methods;
Surgical research methods;
MRI and CT;
Instrumental research methods.

The indications for a particular procedure are the patient’s main complaints and clinical manifestations underlying disease.

differences between screening and diagnostic tests for early case detection

Screening tests are not diagnostic tests

The main purpose of screening tests is to identify early stage diseases (it would be more correct to say that the goal is to identify, i.e., to assess the borderline state between normal and pathological) or risk factors for disease in a large number of apparently healthy people.

The purpose of a diagnostic test is to establish the presence (or absence) of disease as a basis for making treatment decisions in individuals with symptomatic or synergistic symptoms (confirmatory test). Below are some key differences:

Table. Differences between screening and diagnostic tests

	Screening	Diagnostics
Target	To identify potential incidence rates	Establish the presence/absence of the disease
The target audience	Large number of asymptomatic, but potentially at risk persons	Symptomatic patients for diagnosis or asymptomatic patients with a positive screening test
Test method	Simple, acceptable for patients and staff	possibly invasive, expensive, but worthwhile if diagnosis is necessary
Positive result threshold	usually chosen in the direction of high sensitivity so as not to miss potential disease	Selected towards high specificity (true negatives). More weight given to precision and accuracy than patient acceptability
Positive result	Essentially indicates suspicion of disease (often used in combination with other risk factors), thereby warranting confirmation	The result gives a definite diagnosis
Price	Cheap, benefits should justify the cost as large numbers of people will need to be tested to identify a small number of potential cases	Higher costs associated with diagnostic test, may be justified to establish the diagnosis.

Search by case

Case finding is a strategy for targeting resources to individuals or groups suspected of being at risk specific disease. This requires actively seeking out people at increased risk rather than waiting for them to show up at the clinic with symptoms or signs of active disease. Examples of case finding strategies:

Infectious Disease Control

Early case detection is a key control strategy infectious diseases. For example, identifying a sexual partner in syphilis outbreaks, household/work contacts in food outbreaks. The goal is to identify those at risk and offer them screening and follow-up treatment if necessary.

Health systems data

can be used to identify 'missed' risk groups (eg registered GP patients over 50 years of age with a BMI >30 who may not be on the register of people at risk coronary disease hearts)
using population-based data such as the Index of Multiple Deprivation to target interventions in disadvantaged populations
The King's Fund's "patients at risk of readmission" (PARR) software uses patterns in regularly collected data. Data is used to predict that individuals are exposed to more high risk hospitalizations will soon occur next year. The foundation is a think tank that is involved in work related to the health system in England.