The Supreme Court ruling to uphold a decision by parents not to have a heel prick blood test raises both medical and legal issues.
The heel prick test is administered to new-born babies in all of the State's maternity hospitals. It may also be carried out by public health nurses in the community. The test involves taking a tiny amount of blood from the baby's heel - just enough to soak into a small area of test paper - which is then sent for laboratory analysis. Results are available some days later.
Different countries include a range of tests as part of a national screening programme. Advances in modern technology have allowed multiple analysis to take place on a single blood sample.
These tests are aimed at picking up the presence of metabolic diseases which are easily prevented either by hormone replacement or by dietary adjustment.
Hypothyroidism, which results in low levels of thyroid hormone in the body, is easily treated; if not picked up early in the child's life, however, it can cause psychological retardation as well as other ill-effects.
Phenylketonuria arises from a genetic defect in the metabolism of the amino acid phenylalanine. Treatment - which will prevent central nervous system problems later in life - consists of a life-long phenylalanine-free diet.
Galactosaemia is a condition which results from the body's inability to metabolise a form of glucose which is present in milk. A child must be established on milk feeds before it is tested for.
A test that is initially reported as abnormal may on re-testing turn out to be normal. If an abnormality is confirmed then parents will be advised to bring their child to see a specialist in metabolic medicine. Temple Street Children's Hospital in Dublin is the principal centre in the Republic for the treatment of children with metabolic disorders.
Yesterday's decision gives primacy to the fundamental tenet of informed medical consent. Although most parents will be happy for their children to be tested as part of a national programme for the prevention of metabolic disease a parent retains the legal right to refuse investigation or treatment on behalf of a minor.