Confirmatory Testing Considerations – SCID

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Confirmatory Testing
Considerations
BETH VOGEL, MS, CGC
GENETIC COUNSELOR
NEWBORN SCREENING PROGRAM
WADSWORTH CENTER
NEW YORK STATE DEPARTMENT OF HEALTH
Overview
 Implementation
 Short-term follow-up
 Case review meetings
 Diagnostic testing
Implementation: Guidance
 Partnership with clinicians

New York State SCID Consortium
 9 external group members
 National recommendations
 Newborn Screening Translational Research Network, CLSI
Guidelines
Implementation: Guidance
 Discussion points for NBS and clinician group
 Minimum standard confirmatory tests
 Short-term follow-up
 Diagnostic categories
 Transplants
 Algorithm changes
 Detection of non-SCID disorders
Implementation:
Education

Target hospitals and primary care providers
TREC assay is not well known!
 Developed educational materials
 Letter to hospitals
 Phone consultations
 NBS and Specialty Care Centers

WHAT IS A
TREC?!
Short-term Follow-up Process
 Eight Specialty Care Centers
 Referral is called to primary care provider and
specialty care center (SCC)
 Diagnostic form completed by clinician
Case Review Meetings
 Identify topics for Consortium conference calls
 Unusual cases
 Identify need for new diagnostic categories
 Algorithm changes
 Correlation of laboratory findings and clinical outcomes
Case Review Meetings
 Maintain consistency in case closure
 Incidence
 Algorithm changes
 Long-term follow-up
Diagnostic Categories
 From NBSTRN website:
1.
SCID
2.
Leaky SCID/Omenn syndrome
3.
Variant SCID
4.
Syndromes with T cell impairment
5.
Secondary T cell lymphopenia other than preterm alone
6.
Preterm alone
SCID
 Classic phenotype
 <300 autologous T cells/μL
 Emergent treatment required (transplant, gene
therapy, enzyme replacement therapy)
Leaky SCID/Omenn Syndrome
 Low T cell count
 3oo to 1500 T cells/μL
 Requires treatment (transplant, gene therapy,
enzyme replacement therapy)
 Omenn syndrome
 Erythrodermia, hepatosplenomegaly, eosinophilia, elevated
IgE, restricted TCR diversity of T cells
Variant SCID
 Moderately decreased T cell counts
 May not require transplant
Syndromes with T Cell Impairment

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DiGeorge syndrome/22q11.2 deletion syndrome
CHARGE syndrome
Jacobsen syndrome
RAC2 defect
DOCK8 deficiency
Ataxia telangiectasia
VACTERL association
Barth syndrome
TAR syndrome
Down syndrome
Ectrodactyly ectodermal dysplasia syndrome
Other
Secondary T Cell Lymphopenia
Other Than Preterm Alone
 Birth defects
 Gastroschisis, intestinal lymphangiectasia, congenital heart
defects, cardiac surgery +/- thymectomy
 Metabolic disorder, degenerative neuromuscular disease
Preterm Alone
 <37 weeks gestation
 TREC copy number typically improves over time
 If TRECs are undetectable, then full work-up
warranted regardless of gestational age
Idiopathic T-cell Lymphopenia
 Non-SCID
 No congenital anomalies
 Low T-cells that require clinical monitoring
Diagnostic Testing:
Complete Blood Count
 Lymphocytes
 T cells = 70% of circulating lymphocytes
 Proposed as a method to screen for SCID prior to current
technologies
 “ALC (absolute lymphocyte count) <2500/uL in early infancy
requires further evaluation”
• R. Buckley, MD
Diagnostic Testing:
Flow Cytometry
 Evaluation of lymphocyte subpopulations
 Normal ranges vary by age
Diagnostic Testing:
Flow Cytometry
 CD = Cluster of differentiation
Diagnostic Testing: Flow Cytometry
CD
Cell Type
CD3
T cells
CD4
Helper T cells
CD8
Suppressor T cells
CD19
B cells
CD16CD56
NK cells
Diagnostic Testing: Flow Cytometry
Diagnostic Testing:
Lymphocyte Proliferation to Mitogens
 Test of T-cell function

Less sensitive, but more
specific test of T-cell function
 Culture human peripheral
blood mononuclear cells
with plant lectin mitogens)


phytohemagglutinin (PHA),
pokeweed mitogen (PWM),
concanavalin (conA)
Response highest in
newborns and decreases with
age
Diagnostic Testing: Mitogens
Diagnostic Testing:
Naïve and Memory T-cell Count
 Not typically included as part of standard flow
cytometry
 CD45RA+ = Naive
 CD45RO+ = Memory
Genetic Testing
 Multiple genes
 Mutation info often not needed before transplant
 May be important if diagnosis is unclear
 Important for genetic counseling


45% of SCID cases are X-linked (IL2RG-related)
Remainder of the cases are recessive
Diagnostic Form
Diagnostic Form
References
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Hicks MJ, Jones JK, Thies AC, et al: Age-related changes in mitogen-induced lymphocyte
function from birth to old age. Am J Clin Pathol 1983;80:159-163
Baker M, Grossman W, Laessig R, et al. Development of a routine newborn screening protocol
for severe combined immunodeficiency. J Allergy Clin Immunol. 2009; 124: 522-527
Puck M, et al. Population-based newborn screening for severe combined immunodeficiency:
Steps toward implementation. J Allergy Clin Immunol. 2007; 120 (4): 760-768.
Chan K, Puck J. Development of population-based newborn screening for severe combined
immunodeficiency. J Allergy Clin Immunol. 2005; 115: 391-398.
Comeau A, Hale J, Pai S, et al. Guidelines for implementation of population-based newborn
screening for severe combined immunodeficiency. J Inherit Metab Dis. 2010
https://www.nbstrn.org/sites/default/files/SCID%20National%20Monthly%20March%20201
2.pdf
Buckley RH. The long quest for neonatal screening for severe combined immunodeficiency.
Clinical Reviews in Allergy and Immunology. 2012
Adeli MM and Buckley RH. Why newborn screening for severe combined immunodeficiency is
essential: a case report. Pediatrics. 2010; 126(2):e465-e469.
Chase NM, Verbsky JW, Routes JM. Newborn screening for SCID: three years of experience.
Ann. N.Y. Acad. Sci. 2011; 1238: 99-105.
Buckley RH, Transplantation of hematopoietic stem cells in human severe combined
immunodeficiency: longterm outcomes. Immunol Res. 2011; 49: 25-43.
Thank you
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