Newborn Screening for SCID and Other PIDs INGID 2012

Newborn Screening for SCID and Other PIDs

INGID 2012

PID ClassificationInternational Union of Immunologic Societies, 2009

• Combined T and B Immunodeficiencies - 27– Include all forms of SCID

• Predominantly Antibody Deficiencies - 21• Other well defined PIDs – 21

– WAS, DiGeorge s., AT

Challenges of Prompt Diagnosis of SCID

• Rare disease (estimated 100 born annually in U.S.)

• Sporadic cases or family history unrecognized

• Generally, patients appear normal• Early infections may be indistinguishable

from normal infections in infants• Early mortality from infections• Prenatal diagnosis is possible only if family

history and SCID genotype is known

Importance of Early Diagnosis of SCID

• Provide protective isolation– Avoid acquisition of life-threatening and

chronic infections• Avoid live vaccines (rotavirus, BCG)• Afford time to prepare safest and most

effective immune reconstituting therapy

Early vs. Late Diagnosis of SCID*

• Survey of IDF patient database in 2009– Specified SCID diagnosis– Diagnosed by expert center– Autopsy diagnosis consistent with SCID

• 126 families (158 individuals)– 61 deaths confirmed

* Chan et al, 2010

a These infants became symptomatic prior to diagnosis of their SCID. In some of these families a positive family history was ultimately recognized retrospectively.b Definitive treatments in these infants included transplantation or enzyme replacement.

a

b

Chan. Clin. Immunol. 2011

Percentage of families citing particular reasons for not receiving definitive therapy among patients who were diagnosed with SCID, but died without being treated (n=14).


Composition of mortality in SCID patients surveyed.Of the 61 deaths, "Not Diagnosed" were cases of SCID "Not Diagnosed" pre-mortem (dark gray); Diagnosed cases were separated into those who received (white) and those who did not receive (light gray) transplantation or enzyme replacement.


Survival of treated SCID patients. (A) Patients grouped by birth year. All treated patients, solid line (81.4%, n=93); born pre-1995, dashed/dotted line (78.6%, n=28); born 1995–1999 dashed, (75%, n=24); born in 2000 or later, with no difference pre or post 2004, dotted (87.2%, n=41). (B) Patients grouped by treatment type (includes only patients reporting a single treatment, since the order of different treatments was not available); HLA matched sibling HSCT, long-dashed line (93%, n=16); haploidentical T-depleted parent HSCT, short dashed (84%, n=50); adult matched unrelated HSCT, dotted (67%, n=9); matched unrelated cord blood, solid (67%, n=9); and PEG-ADA dashed/dotted (80%, n=5).

Time After Treatment (months) Time After Treatment (months)


Comparison of infant mortality between those groups of neonates who were not tested (n=138, left) and tested (n=20, right) for SCID. Testing was performed only if an affected relative's SCID diagnosis had made parents and medical providers aware of the risk. Proportion of deceased infants is shaded in each pie chart.


Flow chart showing survival outcomes in the 48 probandand 60 sibling cohorts.

Brown. Blood. 2011

Criteria for Newborn Screening

• Important health problem• Detectable at birth• Early treatment improves outcomes• Benefits outweigh risks• Costs balanced against risks

Programmatic criteria considered by the Wisconsin NBS Advisory Committee in evaluating the addition of SCID screening to its NBS test panel

* NBS= newborn screening SCID= severe combined immunodeficiency TREC= T-cell receptor excision circle

Is there a test amenable to routine universal screening of all newborns Yes. The TREC assay on dried-blood spots meets this criterion. with appropriate sensitivity and specificity?

Is the cost per test comparable with other NBS tests? Yes. Preliminary data suggest the cost will be about $6 per child tested

Can the disorder be detected by routine physical exam? No. An SCID baby appears normal at birth.

Does the disorder have a short asymptomatic period after birth? Yes. SCID babies are initially protected by maternal antibodies.

Is the prevalence of the disease 1/100,000 or greater? A conservative estimate of the prevalence of SCID is 1/66,000 births.

Does the disease cause serious medical complications? Yes. SCID is universally fatal if untreated within the first year of life.

Is there a confirmatory test available for SCID? Yes. A lymphocyte subpopulation assessment can be conducted by flow cytometry.

Is there potential for successful treatment? Yes. Successful haematopoietic stem-cell transplantation is curative.

Is access to treatment available to all Wisconsin children? Yes. Two Wisconsin children’s hospitals have active SCID diagnosis and treatment programs.

Does early intervention lead to a better outcome? Yes. Cure rates up to 95% are claimed for babies treated prior to 3.5 months of age

Is a sample available from the current dried-blood spot specimen? Yes. The TREC assay uses a single 3.2-millimeter punch from a dried-blood spot on the NBS card

Is testing equipment available at a reasonable cost? Yes. About $90,000 in capitol equipment is needed to implement a nonautomated assay.

Can the assay be performed on a timely basis and not impede other Yes. Screening results are available within 24 hours, and confirmatory flow NBS reports? cytometry results can be available within days.Are labor requirements for SCID screening comparable with other NBS Yes. Two trained chemists can screen up to 100,000 routine specimens per tests? year.Are clinical consultants available to assist in reporting and interpreting Yes. Clinical consultants associated with diagnostic and treatment facilities at positive screening results to primary care providers? children’s hospitals are part of the Wisconsin SCID-screening program.

Baker. Public Health Rep. 2010

SCID Detection Assay• A small punch is taken from the blood spot on a

standard Guthrie card used for other NBS• DNA is extracted from the 3.2 mm punch• T cell receptor excision circles are enumerated by

RT-qPCR (TRECs)• TRECs cannot replicate, therefore they serve as a

biomarker of naïve T cells that have recently emigrated from the thymus– One specific TREC is produced in approximately 70% of

T cells which express the alpha/beta T cell receptor

Puck. J Allergy Clin Immunol. 2012

SCID Detection Assay

TRECs reflect functional T cells

• If TREC (or KREC) is detected , it is highly likely that the cell (T or B) has successfully created a template for a productive (and unique) T cell receptor or immunoglobulin

• This process underlies the diversity of functional T and B lymphocytes

SCID NBS Assay• TRECs are profoundly reduced in all forms of

SCID– Including cases with maternal engraftment

• TRECS are also reduced in other disorders with poor T cell production (e.g. severe DiGeorge s.)

Results of initial RT-qPCR TREC assay conducted by the Wisconsin NBS Program on 5,766 NBS cards during the 2007 SCID-screening pilot studya,b

aBaker MW, Grossman WJ, Laessig RH, Hoffman GL, Brokopp CD, Kurtycz DF, et al. Development of a routine newborn screening protocol for severe combined immunodeficiency. J Allergy Clin Immunol 2009;124:522-7. Reproduced with permission.b(A) TREC distribution, where the mean is 827 TRECs/3.2-mm DBS and the median is 708 TRECs/3.2-mm DBS; and (B) number of samples with ≤150 TRECs/3.2-mm DBSRT-qPCR = real-time quantitative polymerase chain reactionTREC = T-cell receptor excision circleNBS = newborn screeningSCID = severe combined immunodeficiencymm = millimeterDBS = dried-blood spot


SCID Detection Assay• TREC assay not reliable in premature infants• TREC assay not reliable if drawn from

heparinized catheter• Follow up of deceased premature infants in

Wisconsin with abnormal TREC levels revealed that CODs were generally related to congenital malformations or complications of prematurity

Sample newborn blood screening (NBS) algorithm.Chase. Ann. N.Y. Acad. Sci.

2011

Wisconsin Newborn Screening Program severe combined immunodeficiency screening results, 2008 (n=71,000)


• 507,000 births screened • DNA amplification failures (DAF), <0.08%, requiring second heelsticka

Comparable to other newborn screening assays 56% were <1,500 g at birth 44% had first sample drawn from an indwelling catheter, not a heelstick 84% were in neonatal intensive care units at time of collection

• 50 positive tests, 0.01% of births, required CBC and lymphocyte flow cytometry • 20 follow-up liquid blood samples, 40%, had low T cells confirmed by CBC and flow cytometry • Diagnoses made:

6SCID2 IL-7RA 2 RAG1 2 Common -chain

1 Omenn syndromec due to missense mutations of RAG2 3 SCID variant with no known gene defect 4 Syndromes with T lymphocytopenia

3 DiGeorge (1 complete) 1 Trisomy 21

6 Secondary T lymphocytopenia 2 Gastroschesis 1 Gastrointestinal atresia

3 Prematurity

Summary of California TREC screening experience in the first year

Puck. Ann. N.Y. Acad. Sci. 2011

TREC and KREC copy numbers in dried blood spot samples (DBSS) from anonymized Guthriecards and retested samples and in patients diagnosed with SCID, XLA, AT, NBS, X-HIGM, CVID,or IgAD.

Figure 1

Borte. Blood. 2012

NBS in U.S.• Every state has its own Dept. of Health

which determines NBS– Financial considerations

• (equipment is expensive: >$ 300,000 for Ohio)– Priorities

• U.S. Secretary Sibelius (HHS) supports NBS for SCID

• Ten states currently screening and 5 others to start early 2013

Management of Patients with SCID identified by NBS

(Sullivan,Puck,Routes,Filipovich*)• Issue 1: Low TRECs in prematures

– Repeat until> 37 weeks– If replicate low refer for flow cytometry

• Issue 2: Ideal time interval from abnormal TRECs to immunologic assessment– Less than 2 weeks– Caution family to prevent ill contacts and avoid

live vaccines* J. Clin Immunol, 2012

Management of Patients with SCID identified by NBS

(Sullivan,Puck,Routes,Filipovich)• Issue 3: Ideal time from diagnosis to HCT

– 2 wks. to 4 mos; as soon as dx is confirmed and donor is identified; 3-6 mos.

• Issue 4: If gene defect not known is HCT plan modified to accommodate possible DNA repair defects– Radiation sensitivity testing is available in

California– Reduced Intensity Conditioning

* J. Clin Imunol 2012

Newborn Screening for SCID and Other PIDs INGID 2012

Documents

cases of scid

late diagnosis of scid

scid genotype

tested n

b patients

treated patients

infectionsprenatal diagnosis

birthearly treatment