A study of the neonatal haematology of children with Down syndrome Rebecca James submitted in accordance with the requirements for the degree of Doctor of Philosophy Department of Health Sciences University of York, March 2011 Abstract This thesis describes the establishment and initial findings of the Children with Down Syndrome Study, a birth cohort of children with DS. The Children with Down Syndrome Study was set up in order to characterise the haematology of neonates with Down syndrome and specifically to test the hypothesis that that this differed in this population. The study was carried out with the support of the Down Syndrome Association and the Down Syndrome Medical Interest Group, and through consultation with clinicians and families. Following a pilot study in the Yorkshire region it was established in over 60 hospitals across the north of England. The Children with Down Syndrome Study is the largest birth cohort of children with Down syndrome established to date, and this is the largest reported analysis of the haematology of neonates with Down syndrome. The results confirm that neonates with Down syndrome have a distinct haematological profile. Means and ranges for haematological parameters throughout the neonatal period are provided. The effects of gestational age, birth weight, postnatal age and the venepuncture to processing interval on the neonatal full blood count were examined, and this is the first report of factors that influence the haematological parameters in neonates with Down syndrome. In order to analyse the blood cell morphology a new approach to morphology was developed and validated. Morphological review of samples from neonates with Down syndrome demonstrated that blasts were common. Comparison with automated findings showed that manual review of a film is indicated to look for evidence of transient myeloproliferative disorder. This is also the largest longitudinal study of haematological parameters of children with Down syndrome beyond the neonatal period. The results showed that parameters changed between birth and 1 year, with most being stable thereafter. However, it appears that children with Down syndrome continue to have a distinct morphological profile. 1 Contents Abstract ................................................................................................................................. 1 Contents ................................................................................................................................ 2 List of Figures ........................................................................................................................ 7 List of Tables ......................................................................................................................... 9 Acknowledgements .............................................................................................................. 11 Author’s declaration ............................................................................................................. 12 Chapter 1 Introduction ..................................................................................................... 13 1.1 Purpose ................................................................................................................. 13 1.2 Aims ...................................................................................................................... 14 Chapter 2 Critical assessment of the literature ................................................................ 15 2.1 Introduction ............................................................................................................ 15 2.2 The haematology of neonates with Down syndrome .............................................. 16 2.2.1 Benign haematological changes ..................................................................... 16 2.2.2 Malignant haematological disorders ................................................................ 23 2.2.3 Blood cell morphology .................................................................................... 27 2.3 Existing and historical cohort studies ..................................................................... 28 2.3.1 Summary ........................................................................................................ 28 2.4 Haematological reference ranges for neonates...................................................... 29 2.4.1 Introduction ..................................................................................................... 29 2.4.2 Measurement of haematological parameters .................................................. 30 2.5 Red blood cell parameters in neonates .................................................................. 32 2.5.1 Development of reference ranges for red blood cell parameters ..................... 32 2.5.2 Factors affecting the red blood cell indices ..................................................... 33 2.6 White blood cell parameters in neonates ............................................................... 41 2.6.1 Development of reference ranges ................................................................... 41 2.6.2 Factors affecting white blood cell indices ........................................................ 45 2.6.3 Specific considerations: eosinophils, monocytes, basophils and lymphocytes 49 2.7 Platelet parameters in neonates ............................................................................ 52 2.7.1 Factors affecting neonatal platelet indices ...................................................... 54 2.8 Blood cell morphology in neonates ........................................................................ 58 2.9 Summary ............................................................................................................... 60 Chapter 3 Children with Down Syndrome Study: methods .............................................. 61 3.1 Introduction ............................................................................................................ 61 3.2 Consultation phase ................................................................................................ 62 3.2.1 Consultations with professional stakeholders ................................................. 62 3.2.2 Consultation with clinicians ............................................................................. 62 3.2.3 Consultation with families ............................................................................... 64 3.3 Key points emerging from consultations ................................................................ 65 3.3.1 Consultation with stakeholders ....................................................................... 65 3.3.2 Consultation with clinicians ............................................................................. 66 3.3.3 Consultation with families ............................................................................... 70 3.3.4 Summary of changes to study design following consultation........................... 71 3.4 Study design .......................................................................................................... 72 3.4.1 Study type ...................................................................................................... 72 2 3.4.2 Pilot phase ...................................................................................................... 72 3.4.3 Ethical permission .......................................................................................... 72 3.4.4 UKCRN Portfolio status .................................................................................. 72 3.5 Study setting .......................................................................................................... 72 3.6 Participants ............................................................................................................ 74 3.6.1 Identification of participants: newborn stage ................................................... 74 3.6.2 Action taken after initial recruitment ................................................................ 76 3.6.3 Identification of participants: follow up ............................................................ 77 3.7 Sample collection .................................................................................................. 78 3.8 Data collection ....................................................................................................... 78 3.8.1 Hospital referral form ...................................................................................... 78 3.8.2 Initial questionnaire ......................................................................................... 79 3.8.3 Abstraction from medical records ................................................................... 79 3.9 Sample management ............................................................................................. 80 3.9.1 Processing of neonatal blood samples ........................................................... 80 3.9.2 Processing of follow up blood samples ........................................................... 80 3.10 Data management .............................................................................................. 80 3.10.1 Data management .......................................................................................... 80 3.10.2 Data entry ......................................................................................................