Genetic Screening

GENETIC SCREENING

(1)

The use of such tests in programs that are intended to reach a large percentage of persons who have a particular genetic trait or condition. Goes hand in hand with genetic testing, which main purpose is to screen, choose, or select the genes for proper detection of any genetic disease and other chromosomal activities/ malformities. Genetic screening always involves genetic testing, but genetic testing may not always involve a systematic, organized screening program.

NEONATAL SCREENING: Makes possible the early diagnosis of a disease that can be treated through appropriate medical intervention. Ex. phenylketonuria (PKU)

(1)

Genetic Screening and Counseling The right of married couples to beget children is conditioned by their capability to provide for them. Prospective parents therefore must consider these factors: 1. 2. 3.

their own need to have children as the completion of their mutual love; their own capacity to care for these children; and the risks that each particular child may suffer from grave handicaps that require special care, including the possibility that this child will be faced in its turn with the question of whether he or she should pass on defective genes to the next generation.

Some significant risks of defect exist for every child and could not be eliminated no matter what means would be utilized. Thus, in all cases parents must decide whether they have the capacity to care for a potentially defective child. It is the duty of the genetics counselor and of society to assist the parents in accepting and meeting reasonable risks. (2)

Genetic screening and genetic counseling may occur: before conception of a child, or when the child is still in the womb. Genetic Screening: 1. Amniocentesis 2. Sonography 3. Chorionic sampling: this procedure is less invasive than amniocentesis, enables diagnosis of genetic abnormalities earlier in pregnancy, and thus is less dangerous for the infant. Statistical considerations justifying genetic screening: 1. 2.

3.

There are more than 3,000 single-gene defects identified at present. Each of us carries between five (5) and eight (8) mutant lethal equivalents (genes), which we are all able to transmit to subsequent generations. Thus, we are all mutants, in the strictest sense, although only about 5% to 8% of us actually manifest some forms of genetic mutation. .An estimated 0.5% of all live births are attended by chromosomal imbalances such as trisomies and chromosome maldistributions . . Three quarters of these, or 0.29 %, are deleterious defects. (Also, an estimated 9% of all early embryos are chromosomally abnormal, most of them lethally so.) (3)

4.

Major single-gene mutations – homozygous and heterozygous – such as the autosomal dominants and recessives and the x-linked disorders occur in 1.8% of the general population. The polygenic conditions such as diabetes mellitus, gout, and some allergies occur in 1.7% to 2.6% of all live births. (These figures appear to remain fairly constant throughout the globe.)

5.

Add the figures, and we have the 4.8% to 5% incidence of genetic disease in all live births. In view of the above facts, some scientists in the name of preventive medicine advocate genetic screening of the whole population for four purposes: 1. 2. 3. 4.

(4)

for scientific research, since such research is necessary to achieve full understanding and control over human inheritance; to assist responsible parenthood so that carriers of genetic defects may not pass them on; to make possible early therapy before the malfunctioning of defective genes has caused extensive damage; and to give the parents the option of aborting the child when the defect is serious and no therapy is yet known.

The first three reasons are legitimate but care must be taken not to promote abortion or to cooperate in other ways through direct counseling of abortion. A Catholic health care facility, however, should not be prevented from instituting a pre-conception or post-conception screening program. Such programs must be conducted prudently, since serious questions may be raised: 1.

2.

the research purposes of genetic screening must be regulated in the same way as any other kind of research on human subjects. Proportionate benefits must be considered. most screening techniques used postnatally involve the withdrawal of an insignificant amount of body fluid or tissue and are harmless. Nevertheless, informed consent is required in all such cases.

The use of screening to promote responsible parenthood is in general a laudable purpose, since there can be no doubt that couples should not bring into the world children for whom (with the reasonable assistance of society) they cannot adequately care and that the care of defective children presents special burdens. Consequently, prospective parents have the duty to seek the scientific information useful to such decisions, and society has the duty to assist them in obtaining such information. But extreme caution is necessary if the program Involves negative eugenics. Thus pre-conception genetic screening programs must be carefully designed,

(5)

Guidelines suggested by the Institute of Society, Ethics and Life Sciences for screening programs: 1. 2.

3.

4.

5. 6. 7. 8.

The attainability of program aims should be pretested by pilot projects and other studies, and the program should be constantly evaluated and updated. Community participation in planning and executing the program should be secured to educate the public on the true significance and legitimate use of the information obtained. The information obtained should be made available according to clearly stated policies known to those participating before they consent, and their privacy should be carefully protected. Screening programs should be voluntary. The rights of parents to make their own decisions about the use of the information in family planning should be protected and care taken to avoid stigmatizing them or their offspring. Information about screening should be open and available to all, with priorities given to well-defined populations suffering from frequent defects. Programs should not be instituted unless the tests used are able to give relatively unambiguous information, and thus should be precisely recorded. The general principles with regard to experimentation with human subjects, such as informed consent, protection from risks, and so forth, should be observed. Persons to be screened or have their children screened should be informed before they consent of the nature and cost of therapy and its risks or that no therapy is available.

Counseling to help the subjects understand and deal with the information should be provided.

(6)

Genetic Screening and Counseling The right of married couples to beget children is conditioned by their capability to provide for them. Prospective parents therefore must consider these factors: 1. 2. 3.

their own need to have children as the completion of their mutal love; their own capacity to care for these children; and the risks that each particular child may suffer from grave handicaps that require special care, including the possibility that this child will be faced in its turn with the question of whether he or she should pass on defective genes to the next generation.

Some significant risks of defect exist for every child and could not be eliminated no matter what means would be utilized. Thus, in all cases parents must decide whether they have the capacity to care for a potentially defective child. Furthermore, it is the duty of the genetics counselor and of society to assist the parents in accepting and meeting reasonable risks. For genetics counselors or society at large to encourage in parents the attitude that they should not have children unless the children are perfect and require the least care possible is as reprehensible as to encourage parents to reproduce fatalistically with no account of their genetic compatibility. Genetic screening and genetic counseling may occur before conception of a child, or when the child is still in the womb. (7)

Screening: 1. 2. 3.

Amniocentesis Sonography Chorionic sampling: this procedure is less invasive than amniocentesis, enables diagnosis of genetic abnormalities earlier in pregnancy, and thus is less dangerous for the infant.

Statistical considerations justifying genetic screening: There are more than 3,000 single-gene defects identified as present. Moreover each of us carries between five and eight mutant lethal equivalents (genes), which we are all able to transmit to subsequent generations. Thus, we are all mutants, in the strictest sense, although only about 5% to 8% of us actually manifest some forms of genetic mutation. An estimated 0.5% of all live births are attended by chromosomal imbalances such as trisomies and chromosome maldistributions . . .Three quarters of these, or 0.29 %, are deleterious defects. (Also, an estimated 9% of all early embryos are chromosomally abnormal, most of them lethally so.) Major single-gene mutations – homozygous and heterozygous – such as the autosomal dominants and recessives and the xlinked disorders occur in 1.8% of the general population. The polygenic conditions such as diabetes mellitus, gout, and some allergies occur in 1.7% to 2.6% of all live births. (These figures appear to remain fairly constant throughout the globe.) Add the figures, and we have the 4.8% to 5% inci -idence of genetic disease in all live births. (8)

In view of the above facts, some scientists in the nam Of preventive medicine advocate genetic screening of the whole population for four purposes: 1.

For scientific research, since such research is necessary to achieve full understanding and control over human inheritance; To assist responsible parenthood so that carriers of genetic defects may not pass them on; To make possible early therapy before the malfunctioning of defective genes has caused extensive damage; & To give the parents the option of aborting the child when the defect is serious and no therapy is yet known.

2. 3. 4.

The first three reasons are legitimate but care must be taken not to promote abortion or to cooperate in other ways through direct counseling of abortion. A Catholic health care facility, however, should not be prevented from instituting a pre-conception or postconception screening program. Such programs must be conducted prudently, since serious questions may be

raised: 1.

2.

The research purposes of genetic screening must be regulated in the same way as any other kind of research on human subjects. proportionate benefits must be considered. Most screening techniques used postnatally involve the withdrawal of an insignificant amount of body fluid or tissue and are harmless. Nevertheless, informed consent is required in all such cases. (9)

Hence, the use of screening to promote responsible parenthood is in general a laudable purpose, since there can be no doubt that couples should not bring into the world children for whom (with the reasonable assistance of society) they cannot adequately care and that the care of defective children presents special burdens. Consequently, prospective parents have the duty to seek the scientific information useful to such decisions, and society has the duty to assist them in obtaining such information. But extreme caution is necessary if the program involves negative eugenics. Thus pre-conception genetic screening programs must be carefully designed, thus the following guidelines suggested by the Institute of Society, Ethics and Life Sciences: 1.

2.

3.

The attainability of program aims should be pretested by pilot projects and other studies, and the program should be constantly evaluated and updated. Community participation in planning and executing the program should be secured to educate the public on the true significance and legitimate use of the information obtained. The information obtained should be made available according to clearly stated policies known to those participating before they consent, and their privacy should be carefully protected. (10)

4.

5.

6.

7.

8.

9.

Screening programs should be voluntary. The rights of parents to make their own decisions about the use of the information in family planning should be protected and care taken to avoid stigmatizing them or their offspring. Information about screening should be open and available to all, with priorities given to well-defined populations suffering from frequent defects. Programs should not be instituted unless the tests used are able to give relatively unambiguous information, and thus should be precisely recorded. The general principles with regard to experimentation with human subjects, such as informed consent, protection from risks, and so forth, should be observed. Persons to be screened or have their children screened should be informed before they consent of the nature and cost of therapy and its risks or that no therapy is available. Counseling to help the subjects understand and deal with the information should be provided.

(11)