Neonatal/newborn haemoglobinopathy screening is being performed in an increasing number of European countries since changing patterns of immigration have led to significant numbers of neonates at risk of sickle cell disease. The purpose of screening is to improve management of sickle cell disease through early parental education and the institution of prophylaxis against infection. Some haemoglobinopathy screening programmes are stand-alone, while others are integrated into a neonatal screening programme for metabolic disorders. Despite the logistic problems and economic constraints, neonatal haemoglobinopathy screening is also being gradually introduced in a number of African countries.
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This issue of the Journal of Clinical Pathology includes a series of articles on neonatal screening for haemoglobinopathies. Screening is a public health service in which a test or enquiry is systematically applied to a defined population to identify individuals who have not sought medical attention but who are at sufficient risk of a specified disorder to warrant further investigation or treatment.1 2 In the context of neonatal haemoglobinopathy screening, the aim is usually the early identification and effective management of sickle cell disease. Such screening has assumed increasing importance in Europe in recent decades, as patterns of immigration have changed, leading to there being populations at risk of serious haemoglobinopathies in many European countries. Such migration became significant in some countries after the Second World War but has accelerated and become a more general phenomenon in the last 10–15 years. There remain European countries where screening is not indicated. For example, Cyprus has a highly effective premarital screening programme for β thalassaemia and a very low prevalence of sickle cell disease so that neonatal screening is not required. There are, however, European countries in which sickle cell disease occurs but where no neonatal screening programme has yet been introduced.
Screening has always been relevant in countries where such diseases are endemic but their health services, with limited resources and a large burden of disease, have often had higher priorities. However pilot studies have been carried out and, in some cases, screening has commenced in African countries including Ghana, Nigeria, Burkina Faso, Cameroon, Guinea-Bissau, Burundi, Rwanda, Democratic Republic of the Congo and Sudan, and also in India and Brazil.3–8
PURPOSE OF NEONATAL HAEMOGLOBINOPATHY SCREENING
Screening is aimed at the detection of sickle cell disease (box 1); this meets the criteria for introduction of a screening programme. Screening followed by definitive diagnosis means that optimal care can be offered to the affected child. However, follow-up of infants with little or no haemoglobin A will also lead to the detection of babies with β thalassaemia major. Compound heterozygosity for haemoglobin E and β thalassaemia will also be detected. Cases of haemoglobin H disease may be detected and there will also be incidental detection of many babies with clinically insignificant (but potentially genetically significant) heterozygosity for a variant haemoglobin. The genetic characteristics in parents that might give rise to a condition of clinical significance in a child are summarised in fig 1.
Box 1: Conditions likely to be detected in neonatal haemoglobinopathy screening
Conditions at which programmes are usually directed
Sickle cell anaemia (homozygosity for haemoglobin S)
Sickle cell/haemoglobin C disease
Sickle cell/β thalassaemia
Sickle cell/δβ thalassaemia
Sickle cell/haemoglobin D-Punjab disease
Sickle cell/haemoglobin O-Arab disease
Sickle cell/haemoglobin Lepore disease
Sickle cell/haemoglobin E disease (clinically mild)
Sickle cell/hereditary persistence of fetal haemoglobin (clinically very mild but needs to be distinguished from compound heterozygosity for haemoglobin S/δβ thalassaemia)
Conditions that may be detected but at which programmes are not usually specifically directed
β Thalassaemia major and intermedia
Haemoglobin H disease
Heterozygosity for α° thalassaemia or homozygosity for α+ thalassaemia (in some circumstances)
Heterozygosity for variant haemoglobins
Conditions that will not be detected
β Thalassaemia heterozygosity
PREVALENCE OF HAEMOGLOBINOPATHIES
The likelihood of finding a significant haemoglobinopathy in a neonate in various European countries is shown as estimated prevalence of conceptions with a combination of significant globin gene disorders (table 1).9 This table also permits some deductions as to the type of abnormality likely to be found in the fetus, on the basis of estimated prevalence rates of globin gene disorders in pregnant women. Estimates for prevalence of haemoglobin S and haemoglobin E are shown separately (the latter being relevant because it may interact with β thalassaemia leading to thalassaemia intermedia or major). Other variant haemoglobins, such as haemoglobin C and haemoglobin D (which will include haemoglobin D-Punjab), that may interact with haemoglobin S to cause sickle cell disease have been aggregated.
The likelihood that a relevant abnormality in a fetus will lead to the birth of a baby with a significant haemoglobinopathy depends on the nature of the predicted abnormality, since in many European countries prediction of β thalassaemia major usually leads to termination of pregnancy, whereas this is much less likely to occur when sickle cell disease is predicted.
PURPOSE OF SCREENING FOR SICKLE CELL DISEASE
The purpose of neonatal screening for sickle cell disease is to be able to offer optimal management from earliest infancy. Such optimal management includes (i) vaccination against infection by Streptococcus pneumoniae (7-valent conjugate pneumococcal vaccine), Haemophilus influenza type b (conjugate vaccine) and meningococcus type C (conjugate vaccine), (ii) administration of prophylactic penicillin from 12 weeks of age, and (iii) education of parents to facilitate early detection of infections, splenic sequestration and other complications of sickle cell disease. The standard of care in developed countries may soon also include transcranial Doppler screening to predict stroke and to institute prophylactic transfusion when indicated. In sub-Saharan African countries malaria prophylaxis should be administered and other antimalaria measures adopted since malaria is a significant cause of morbidity and mortality in sickle cell disease.10 The effectiveness of neonatal screening programmes, when integrated into good paediatric services and coupled with parental education and support, has been shown in the USA,11–14 Jamaica15 16 and the UK.17
SELECTION OF BABIES FOR NEONATAL TESTING
A neonatal haemoglobinopathy screening policy can seek to test all babies or to screen by assessment of the parents so that testing is more selective. Testing may be offered for (i) babies of at-risk couples, (ii) babies of known carriers of a variant haemoglobin, (iii) babies of mothers from at-risk ethnic groups, or (iv) all neonates. Policy varies greatly between countries and depends on prevalence of variant haemoglobins and on funding.
Choices of sample and laboratory methods applicable for neonatal screening are not necessarily the same as those used for haemoglobinopathy diagnosis in children and adults. It is possible to use an anticoagulated cord blood sample; this provides a high-quality sample (as long as maternal contamination is avoided) but does create logistic difficulties. Such samples are suitable for analysis by any standard method (eg, haemoglobin electrophoresis on a cellulose acetate membrane, acid agarose electrophoresis, high-performance liquid chromatography, isoelectric focusing or capillary zone electrophoresis). In European countries with well-developed programmes for screening for other inherited conditions, such as phenylketonuria and neonatal hypothyroidism, logistics are usually more straightforward if a haemoglobinopathy screening programme is integrated into the general screening programme, which varyies between countries but is usually carried out around 3–10 days of age. In this case, the sample available is a capillary blood sample obtained by heel prick and preserved as a dried blood spot on filter paper (a “Guthrie spot”). In comparison with a cord blood sample, this leads to a smaller sample with some degradation of haemoglobin. Haemoglobin electrophoresis is then unsuitable but high-performance liquid chromatography and isoelectric focusing remain applicable. Whether a liquid or dried sample is used, the nature of any provisionally identified haemoglobin requires confirmation by a second technique. Because of the low percentage of the variant haemoglobin, a sickle solubility test is totally inappropriate in the neonatal period. Particular problems arise if a baby has been transfused either in utero or in the neonatal period before obtaining a capillary sample. The options then available are to recall the baby for further testing after an appropriate interval of time or to test for a specific abnormality by DNA analysis.
Newer laboratory methods under development with the potential for use in neonatal diagnosis include tandem mass spectrometry18 and enzyme-linked immunosorbent assay, using a monoclonal antibody that detects haemoglobin S and haemoglobin C, applicable for detection of sickle cell disease.6 19
DETECTION OF ABNORMALITIES OTHER THAN SICKLE CELL DISEASE
Any baby with haemoglobin F only should be followed up since there is a possibility of β thalassaemia major, particularly if the baby is full term. Likewise, follow-up of babies with haemoglobin E and no haemoglobin A or with haemoglobin E in excess of haemoglobin A will lead to the detection of compound heterozygosity for haemoglobin E and β thalassaemia, a compound heterozygous state that often leads to β thalassaemia intermedia or major.
Haemoglobin H disease can be also suspected because of a high percentage of haemoglobin Bart’s. In some countries such babies are followed up and parents are investigated because there is a high probability that one parent has α0 thalassaemia heterozygosity. However, it should be noted that if one parent has α0 thalassaemia heterozygosity and the other has α+ thalassaemia heterozygosity there is no risk of haemoglobin Bart’s hydrops fetalis in a subsequent pregnancy. Investigation of families is not mandatory since in most countries prenatal diagnosis of haemoglobin H disease is not considered indicated; haemoglobin H disease is usually not of such severity that termination of pregnancy would be justified.
Other globin gene abnormalities, some of potential genetic significance, may be detected on neonatal screening. Such abnormalities include heterozygosity for haemoglobins S, C, D-Punjab, O-Arab, Lepore and, if fresh blood rather than a dried blood spot is used, α0 thalassaemia.20 Detection of any of these in a neonate gives information that is likely to be relevant to future pregnancies in the mother. Information as to their nature and significance should therefore be given to the mother as well as to the general practitioner. On other occasions a variant haemoglobin is found that is unlikely to be clinically significant. Whether such abnormalities should be followed up with results being explained to the parents and primary care provider is controversial, and practice varies between countries and even between different centres in the one country. Policy depends in part of work load and adequacy of funding, although the possibility of provoking unnecessary anxiety has also to be considered.
Clinicians receiving results of neonatal screening should be aware that β thalassaemia heterozygosity is not detected by testing during this period of life.
INTEGRATING OF NEONATAL SCREENING WITH OTHER SERVICES
It is highly desirable that neonatal and antenatal screening programmes are integrated and that the discovery of a child with sickle cell disease is not what first reveals the carrier status of the parents. The discovery of a genetically significant haemoglobin variant or thalassaemic condition in a neonate is an indication to offer testing to both parents, if this has not already been done.
Integration of neonatal screening with child health services is essential if neonatal screening is to lead to improved outcomes.
Sickle cell disease is now the most prevalent serious inherited disease in Europe. Neonatal screening with subsequent optimal management of the infant significantly reduces the morbidity and mortality. Neonatal screening programmes are required in all western and most southern European countries. Other globin gene abnormalities, some of potential genetic significance, may be detected in neonatal screening. How the nature of such conditions should be confirmed and how or if the information should be conveyed to parents requires consideration. Neonatal haemoglobinopathy screening also has the potential to reduce morbidity and mortality of sickle cell anaemia in high-prevalence African countries.
This themed issue of the Journal of Clinical Pathology has been planned in collaboration with the European Network for Rare and Congenital Anaemias (http://www.enerca.org/).
Competing interests: None.
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