Genetic screening: ethical issues - Nuffield Council on Bioethics
Genetic screening: ethical issues - Nuffield Council on Bioethics
Genetic screening: ethical issues - Nuffield Council on Bioethics
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16<br />
3.3 Individuals with a family history of an inherited disorder may<br />
undergo genetic testing. Such testing should be distinguished<br />
from populati<strong>on</strong> <str<strong>on</strong>g>screening</str<strong>on</strong>g>, but has important similar societal<br />
effects which are c<strong>on</strong>sidered in this report. Family studies provide<br />
the most practical strategy for detecti<strong>on</strong> of the abnormal gene in<br />
most dominantly inherited and X-linked disorders.<br />
3.4 Screening programmes often have more than <strong>on</strong>e comp<strong>on</strong>ent. A<br />
primary screen may be offered to all members of the populati<strong>on</strong><br />
to identify a ‘risk group’, which would then be offered further<br />
testing, leading to definitive diagnosis. This sequence applies<br />
to many genetic <str<strong>on</strong>g>screening</str<strong>on</strong>g> programmes, depending <strong>on</strong> the<br />
methodology used. For example, the initial <str<strong>on</strong>g>screening</str<strong>on</strong>g> test for<br />
phenylket<strong>on</strong>uria (PKU) is by an indirect method (see paragraph<br />
2.16). Babies with a positive result do not always have the<br />
disease and further tests are required to c<strong>on</strong>firm the diagnosis.<br />
Where, however, direct methods are better (for example, testing<br />
for carriers for cystic fibrosis) no further testing is required for<br />
those with positive results. In the case of cystic fibrosis, a small<br />
proporti<strong>on</strong> of individuals whose genetic defect is not detected by<br />
the current test will be missed.<br />
3.5 Depending up<strong>on</strong> the mode of inheritance, the genetic abnormality,<br />
and the type of test, <str<strong>on</strong>g>screening</str<strong>on</strong>g> may detect individuals:-<br />
(i)<br />
(ii)<br />
(iii)<br />
who have the disorder, for example, phenylket<strong>on</strong>uria (PKU)<br />
as presently screened by blood spot in the newborn;<br />
who are themselves unaffected, but are carriers of a gene<br />
for a recessively inherited disorder (for example, sickle cell<br />
disease) and thus at risk of having an affected child;<br />
who may themselves develop a disease after many years,<br />
for example, Huntingt<strong>on</strong>’s disease.<br />
It follows that a variety of different practical and <str<strong>on</strong>g>ethical</str<strong>on</strong>g> problems<br />
may arise.<br />
3.6 Screening may also be carried out for c<strong>on</strong>genital disorders<br />
where a genetic basis may exist but has not been established; for<br />
example, ultrasound scanning of a fetus for malformati<strong>on</strong>s.<br />
3.7 In the future, increased understanding of the genetic comp<strong>on</strong>ent<br />
in comm<strong>on</strong> diseases may lead to proposals for <str<strong>on</strong>g>screening</str<strong>on</strong>g> for<br />
genetic abnormalities that c<strong>on</strong>fer an increased risk for the<br />
individual rather than a certainty of developing the disease : for<br />
example, <str<strong>on</strong>g>screening</str<strong>on</strong>g> may point to an increased risk of cancer, or<br />
diabetes, or mental disease and there may not be simple or<br />
guaranteed ways of avoiding the risk or of treating the c<strong>on</strong>diti<strong>on</strong>