SCID: spotting the danger

22 July 2021

Lauren Cooper, Lucy Pylypiw and Liz Robinson of the NHS Newborn Blood Spot screening programme explain how an evaluation of screening for severe combined immunodeficiency will work, and what HVs can do.

From September 2021, the NHS newborn blood spot (NBS) screening programme will begin an evaluation of screening for severe combined immunodeficiency (SCID) in six centres in England.

SCID is a group of rare, inherited conditions that impair development of the immune system. About 1 in 40,000 babies born in England is born with SCID. Without early recognition and treatment, babies with SCID generally die before they reach a year of age (van der Burg and Gennery, 2011).

All babies up to a year of age are currently offered NBS screening for nine other conditions (Public Health England (PHE), 2018a):

  • Congenital hypothyroidism
  • Cystic fibrosis
  • Glutaric aciduria type 1
  • Homocystinuria
  • Isovaleric aciduria
  • Maple syrup urine disease
  • Medium-chain acyl-CoA dehydrogenase deficiency
  • Phenylketonuria
  • Sickle cell disease.

When the baby is five days old, a blood spot sample is taken from its heel and collected on a specially designed card. The sample is then sent to a regional laboratory for testing. Community midwives, neonatal nurses or maternity care assistants usually take the sample. The sample can also be taken by a health visitor if a baby moves into England when it is under a year old.

The SCID evaluation will take place in two-thirds of the country over a two-year period. In the areas taking part, screening for SCID will be offered as part of the existing NBS screening programme, using the same blood spot sample.

HVs will play an important role by contacting families who move into an SCID screening area as soon as possible. If NBS screening has been completed, no further action is needed. If not, screening for SCID should be offered alongside NBS screening if the baby is in a SCID screening area.


What is SCID?

SCID is very rare disease that affects the immune system, leading to reduced and  malfunctioning numbers of T and B lymphocytes. These are specialised white blood cells made in the bone marrow and thymus gland that help to fight infection. Illnesses that are not serious for most babies can be life-threatening for babies with SCID (van der Burg and Gennery, 2011).

About one in 40,000 babies born in England is born with SCID (about 14 babies a year). It is more common in some black and ethnic populations and consanguineous families (those in which the parents are biologically related) (Al-Mousa et al, 2018; Sanchez et al, 2007). About one-third of cases are diagnosed because of a family history, but the delay in identifying the remainder means that these babies are exposed to infections for longer before receiving treatment. This delay can make these babies very sick, increases mortality and morbidity, and reduces the success of treatment (Brown et al, 2011).

How the evaluation works

The evaluation will help us to determine whether screening for SCID works in practice as part of the existing NBS screening programme.

The evaluation will begin on 6 September 2021 and will take place over two years. Screening for SCID will then continue while the evidence is reviewed and the UK National Screening Committee decides whether to recommend screening for the condition as part of the national programme.

The areas taking part are those covered by the screening laboratories in London (Great Ormond Street Hospital and Guy’s and St Thomas’ Hospital), Manchester, Birmingham, Newcastle and Sheffield.

In these areas, families will be offered SCID screening for their baby. If screening is accepted, the blood spot sample will be taken in the usual way and tested for SCID as well as the other conditions.

Babies will have one of three results:

  •  ‘SCID not suspected’ – indicating that the baby is very unlikely to have SCID
  •  ‘SCID suspected’ – indicating that the baby may have SCID or a similar condition which affects the immune system
  •  ‘SCID screening not offered’ – indicating that the baby had NBS screening in a non-screening area, so was not screened for SCID.

Babies with a ‘SCID suspected’ result will be referred immediately to regional immunology services for diagnostic testing. The test can also detect other conditions.

Diagnostic testing will confirm if the baby:

  • Does not have SCID or another condition, and can be discharged
  • Has SCID
  • Has another condition affecting the immune system.

Maternity and health visiting services will not need to collect any new data.

Changes to the BCG vaccination programme in England

From 1 September 2021, the BCG vaccine will only be offered to eligible babies from four weeks of age where a baby has a ‘SCID not suspected’ or ‘SCID screening not offered’ result.

This change is necessary because the BCG is a live vaccine and can make treatment for SCID more complicated. Changes to the BCG vaccine service will also improve the uptake of the BCG vaccine, which is targeted at specific groups (PHE, 2018b).

What do you need to do if you are a health visitor?

  • If you are in an area that will be taking part in the evaluation:
  • Contact families that move into your area as soon as possible to confirm that, if they have a baby under one year of age, they have a valid NBS result. If so, no further action is needed.
  • If the baby does not have a valid NBS result, offer screening for all the conditions, including SCID. Give parents information on all the conditions to help them make an informed choice.
  • Clearly mark any declines for SCID on the blood spot card (parents can still choose screening for the other conditions).
  • It’s important to note any family history of SCID or use of immunosuppressant drugs in pregnancy on the blood spot card.
  • There is no need to take a different sample – just take four good quality blood spots and complete the card accurately (PHE, 2016)
  • Remember to record if the sample is a repeat.

Lauren Cooper is project lead (SCID/BCG/cystic fibrosis next-gen sequencing); Lucy Pylypiw is project lead; and Liz Robinson is programme clinical projects coordinator SCID.


Resources

New resources for families and professionals bit.ly/PHE_SCID_blog

A new e-learning resource on SCID that includes information about taking consent, bit.ly/PHE_SCID

Updates on the evaluation bit.ly/PHE_screen_blog


References

Al-Mousa H, Al-Dakheel G, Jabr A et al. (2018) High incidence of severe combined immunodeficiency disease in Saudi Arabia detected through combined T cell receptor excision circle and next generation sequencing of newborn dried blood spots. Frontiers in Immunology 16(9): 782.

Brown L, Xu-Bayford J, Allwood Z et al. (2011) Neonatal diagnosis of severe combined immunodeficiency leads to significantly improved survival outcome: the case for newborn screening. Blood 117(11): 3243-246.

Gennery AR, Slatter MA, Grandin L et al. (2010) Transplantation of haematopoietic stem cells and long-term survival for primary immunodeficiencies in Europe: Entering a new century, do we do better? Journal of Allergy and Clinical Immunology 126(3): 602-10.

Public Health England. (2018a) Newborn blood spot screening: programme handbook. See: gov.uk/government/publications/health-professional-handbook-newborn-blood-spot-screening  (accessed 22 June 2021).

Public Health England. (2018b) Tuberculosis: the green book, chapter 32. See: gov.uk/government/publications/tuberculosis-the-green-book-chapter-32 (accessed 22 June 2021).

Public Health England. (2016) Guidelines for newborn blood spot sampling. See: gov.uk/government/publications/newborn-blood-spot-screening-sampling-guidelines (accessed 22 June 2021).

Sanchez J, Monaghan G, Borsting C et al. (2007) Carrier frequency of a nonsense mutation in the adenosine deaminase (ADA) gene implies a high incidence of ADA-deficient severe combined immunodeficiency (SCID) in Somalia and a single, common haplotype indicates common ancestry. Annals of Human Genetics 71(3): 336-47. 

Van der Burg M, Gennery AR. (2011) Educational paper. The expanding clinical and immunological spectrum of severe combined immunodeficiency. European Journal of Pediatrics 170(5): 561-71.

Image Credit | Shutterstock

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