Introduction Biochemical screening of newborns in some parts of uk since 1980

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Introduction

  • Biochemical screening of newborns in some parts of UK since 1980

  • Northern Ireland since 1983, Wales 1997, Scotland 2003.

  • Parent-led support group driven towards extension of screening for all newborns in UK

  • National Screening committee not convinced of benefits of screen but supported it because of inequity in UK

  • Evidence that early treatment leads to better outcome is accumulating

  • Screening in all areas of England from 1 October 2006



Screening protocol for England

  • IRT–DNA–IRT (5-8 days. Raised >99.5th centile)

  • Maximise diagnosis of affecteds with preventable / treatable disease

  • Minimise pick up of carriers and mild forms (late onset, unpreventable)

  • Stage 1: 4 mutations

  • Stage 2: 29/30 mutations

  • (detects 85-90% mutations in Caucasians)

  • 2nd IRT intended to increase detection of CF

  • Disadvantages – pick up healthy carriers, non-paternity





UK regional laboratories

  • England: 1st screen, 4 mutations

  • c.489+1G>T, p.Phe508del, p.Gly542X, p.Gly551Asp

  • 2nd screen, 29 mutations

  • Wales (Cardiff): 1 screen, 8 mutations

  • c.489+1G>T, p.Phe508del, p.Gly542X, p.Gly551Asp

  • p.Gly85Glu, p.Arg553X, c.1766+1G>A, p.Arg1283Met

  • Scotland (Glasgow): 1 screen, 28 mutations

  • Birmingham –

  • 1st screen West Midlands Newborn Screening Centre

  • 2nd screen West Midlands Regional Genetics Service



Cystic Fibrosis Regional Genetics Screening Laboratories Laboratories

  • North West Thames

  • Bristol

  • Wessex

  • Oxford

  • Cambridge

  • Birmingham

  • Trent

  • Manchester

  • Liverpool

  • Leeds

  • Newcastle



Methods and reporting

  • Extraction: EZ1, boiled prep, OLA CF33,

  • QIA Amp® DNA micro kit

  • Methods: Tepnel® CF4, CF29, CF-HT30,

  • CF-HT28, Abbot® CF OLA33, in-house Taqman, PCR + PAGE, sequencing exons 4 & 11

  • Sample: whole card (7), punches (3), 1 spot, 1 square. Storage issues (2).

  • Reporting method: variable

  • Turnaround: almost all report >97% in 4 days



A blood spot card



CF screening numbers



CF screening numbers



CF screening numbers



CF screening numbers



CF screening numbers



Babies presumed affected



Babies presumed affected



Babies presumed affected



Babies presumed affected



Babies presumed affected



Babies presumed affected (% of babies with raised IRT)



Babies with 1 mutation



Babies with 1 mutation



Babies with 1 mutation



Babies with 1 mutation



Summary of mutations found in affected babies (panel 1 and panel 1+2)



Meconium ileus cases

  • Echogenic screen showed pregnancy to be F508del/F508del – family told predicted CF affected.

  • Baby included in CFNS and had normal IRT - reported as “CF not suspected”. Checked Guthrie for F508del and confirmed original results. Biochem then lowered their cut off levels slightly to try and prevent this happening again.

  • Baby with meconium ileus was missed on blood spots as no raised IRT – had F508del and R117H/5T

  • Urgent direct referral from a neonatal unit for a child with meconium peritonitis. Screened for the full panel of mutations and identified a c.3528delC heterozygote. Guthrie analysis reported this patient as ‘no mutation detected’ for four mutations. (Received in time frame)



R117H cases

  • Communication issue regarding F508del/R117H (7T/9T) compound heterozygote.

  • 2 cases of F508del/R117H mutations. No guidance in CFNS for polyT analysis so not carried out on Guthrie referrals. Subsequent confirmatory blood samples requested PolyT analysis and both patients proved to be 7/9T. (These cases have been identified since 31/03/07)

  • Case NOT detected by CFNS:

  • Mother affected: Phe508del / rare mutation,

  • Father carrier: R117H / N.

  • Baby born with R117H / rare mutation.

  • 1st IRT well below 99.5th C so not sent for DNA.

  • Sweat test and subsequent management not yet known.



  • F508del carrier picked up on CFNS. Cascade testing of family revealed 2 yr old cousin was F508del/R117H(7T) and had borderline sweat test. Being treated for CF.

  • F508del / D1152H identified in a CFNS case. Subsequent testing of siblings. Both F508del / D1152H compound heterozygotes.

  • One asymptomatic but one who had presented with a cough and small size and had been discharged.

  • Infant with F508del / 2789+insA on CFNS. 17 yr old brother (asymptomatic) requested testing.

  • Also F508del / 2789+insA and had positive sweat test.



Technical problems

  • False positive F508del/F508del using the CF30HT kit.

  • Reported to Tepnel and they subsequently located a polymorphism under normal F508del primer binding site. Now confirm all F508del homozygotes with alternative assay and different primers. All other homozygous mutations are confirmed by requesting parental samples.

  • One copy of F508del and no second mutation.

  • Sent to Manchester for rare mutation screen. Found R117H. Checked data again – no evidence of blue mutation peak on CFHT, but drop in height of green normal peak. Repeated blood spot and fresh blood sample, still no blue mutation peak. Contacted Tepnel.

  • Blood spot QA from CDC USA - CFHT kit failed to detect W1282X mutation. Informed Tepnel.



Problems / suggestions

  • Samples – variable quality, size, timing.

  • More referrals than predicted – cut off too low?

  • Lack of follow-up e.g. 2nd IRT data, 2nd rare mutation

  • Need to have a system for prenatal tests to pre-empt CFNS to avoid conflicting reports.

  • Regions with significant non-Caucasian population – 4 mutation panel not ideal e.g. NW Thames would like W1282X as large Ashkenazi

  • Use the same protocol as CFNS for all diagnostic CF referrals



Summary

  • National CF Newborn Screening programme going well after first year

  • Good communication with Biochemistry

  • Higher workload than expected

  • Lower pick up rate than expected (affecteds and carriers)

  • More babies with 0 mutations and 2nd high IRT than in algorithm. May not get full screen.

  • Need to have system for prenatal results

  • Would like more feedback about fate of cases with unclear outcome.



Acknowledgements

  • Glasgow

  • Cardiff

  • North West Thames

  • West Midlands

  • Bristol

  • Leeds

  • Liverpool

  • Manchester

  • Oxford

  • Trent

  • Newcastle

  • Wessex




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