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What’s being screened in Wolverhampton ?

(Original title: Why was my baby screened?)

At birth the midwife takes a blood test from the placenta. This blood sample from the placenta is referred to as a "cord blood sample". Approximately five to six days after the birth another blood sample is taken from the heel of the baby's foot. This blood sample is used in the 'Heel-Prick Test' (also called: Neonatal Screening or Guthrie Card Test). These blood samples are used to test for various disorders. Babies are tested for the following specific conditions:

Phenylketonuria (PKU) is a rare inherited condition from both parents. Six days of milk feed is required before this particular test can be administered. It occurs in 7 out of every 100,000 live births. Babies who are found to have this condition cannot deal with the protein phenylalanine found in every day foods such as milk, eggs, fish cheese and meats. A high build-up of this protein in the baby's brain tissue can lead to serious damage causing mental retardation. Babies found to have this condition are put on a special diet so that they can grow and develop normally. ⁽²⁾

Congenital Hypothyroidism is a rare condition, which occurs in 29 out of every 100,000 live births. Congenital means the baby was born with the condition. Hypothyroidism means that the thyroid gland found behind the 'Adams apple' in the neck is not producing enough of the hormone thyroxine. If this condition is not detected the baby will not develop normally and this will lead to mental retardation. The treatment is simple and effective. Babies are given thyroxine in the form of a crushed tablet. As with PKU, these babies go on to grow and develop normally.⁽²⁾

Sickle Cell Disease (SCD) is a rare group of inherited conditions from both parents. It occurs in 25 out of every 100,000 live births. This disorder means that the red blood cell is prone to changing shape to that of a crescent or sickle shape and sticking together (sickling). Repeated sickling and unsickling permanently damages the blood cell, becoming dehydrated and irreversibly sickled. The blockage of small blood vessels occurs, resulting in a painful "crisis" and a variety of complications can occur. SCD is variable and unpredictable in severity. Main symptoms are pain, anaemia and increased risk of infection. There is a high rate of mortality in children aged between 1 to 3 years, owing to these problems and overwhelming pneumococcal infection. The management of SCD is based on routine prophylaxis of penicillin for infants (which reduces infection rates by 84%), the early identification of complications and education for carers for example eating a well balanced diet, drinking plenty of fluids e.g. 5 glasses per day, and advice regarding general anaesthesia ^{(1, 6)}.

Disorder (Disease)	Live Births Per 100,000 for All Populations	*Conceptions Per 100,000 for:
Phenylketonuria (PKU)	7
Congenital Hypothyroidism	29
Sickle Cell Disease (SCD)	25	28 (All Population) 30-70 (Cypriot) 560 (Black Caribbean) 8 (Indian)
Beta-Thalassaemia Major or Intermedia	3	7 (All Population) 1.8 (Black Caribbean) 384-640 (Cypriot) 16-51 (Indian)

*Conceptions are not the same as live births because a number of women will decide to abort (Selective termination of 50-70% of foetuses with Beta-Thalassaemia and 5-15% of those with SCD).⁽¹⁾

Beta-Thalassaemia Major or Intermedia is a rare inherited condition from both parents. It occurs in 3 out of every 100,000 live births. In Wolverhampton the parents of the baby who has had a cord blood test is also informed that a thalassaemia investigation cannot be done until the baby is 12 months of age. This is because it is difficult to make a definite diagnosis of thalassaemia trait at such an early stage. Beta-thalassaemia major however can be diagnosed within 3 months of life. There are tests that can be done before birth (pre-natal diagnosis). During pregnancy, beta-thalassaemia major does not affect the foetus. This is because the foetus has a special sort of haemoglobin (the red-stuff found inside blood cells that gives blood its colour), called "foetal haemoglobin" (HbF). Children and adults have different haemoglobin called "adult haemoglobin" (HbA). When a baby is born it has a very high level of HbF, which is gradually replaced by HbA. This gradual change can take around 6-12 months. Therefore children with thalassaemia major are well at birth (3). The problem with thalassaemia major is that the child cannot make enough HbA. The main treatment is regular blood transfusions (usually every 4 weeks). Transfusions are accompanied by regular desferrioxamine infusions to prevent iron overload. (3) The spleen can become too active and begin to destroy red blood cells (hypersplenism), therefore transfusion becomes less effective. Then it may become necessary to take the spleen out (splenectomy). For a well-treated patient growth and development (especially bones of the face) is normal. However a chronic disease always causes some limitation of the quality of life, especially when it requires frequent and complex treatment. ⁽³⁾

At the present moment in Wolverhampton the Heel-Prick test is used to identify the PKU and congenital hypothyroidism. The cord sample is used to check for healthy carrier state such as sickle cell trait and the disease state such as sickle cell anaemia. Thalassaemia investigations for thalassaemia trait cannot be performed until the child is 12 months of age.

It is the responsibility of the lead maternity carer to explain what the test may indicate before the blood sample is taken. Educating the patient with information regarding the purpose of the test and the procedures involved will assist the patient in understanding and hopefully reduce any pre-existing anxiety. There should be no pressure on couples to accept such testing.^{(4, 5)}

Reference:

(1) Davies SC, Cronin E, Gill M, Greengross P, Hickman M, Normand C, Screening for sickle cell disease and thalassaemia: a systematic review with supplementary research. Health Technology Assessment 2000; Vol 4: No. 3, pp 1-7, 27-32.

(2) The Heel-Prick Test: blood screening tests for babies. A leaflet by The Birmingham Children's Hospital NHS Trust. Forms UK plc, FCN163951/01.

(3) Vullo R, Modell B, Georganda E, What is thalassaemia?: fighting for the red in blood. 1995, 2nd Edition, Printed and Distributed by The Thalassaemia International Federation. Pp 15-20.

(4) Women's Health Action: events reports 2000 onwards.

http://www.womens-health.org.nz/2000evreps.htm last accessed 31 May 2001.

(5) Information giving and decision making in ante-natal screening. Contributor: Joanie Dimivicius. http://www.prochoiceforum.org.uk/and2.htm last accessed 31 May 2001.

(6) Note: Statistical figures for sickle cell and thalassaemia were confirmed best estimates by the London Health Observatory, King's Fund, 11-13 Cavendish Square, London, W1G 0AN. Reference 1 (above) was used by LHO.