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Laboratory Perspective of Laboratory Perspective of screening screening

Joan HenthornJoan Henthorn

Central Middlesex HospitalCentral Middlesex Hospital

London UKLondon UK

July 2009July 2009

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Screening Screening versusversus Diagnosis Diagnosis

Screening – systematic testing of a whole Screening – systematic testing of a whole or selected population or selected population Uses fast throughput techniqueUses fast throughput technique Often used to target certain conditionsOften used to target certain conditions

Diagnosis – the intensive investigation of a Diagnosis – the intensive investigation of a individual or family using many different individual or family using many different techniques to arrive at a conclusiontechniques to arrive at a conclusion

All screening

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AIMS OF SCREENINGAIMS OF SCREENING

NEONATALNEONATALTo detect individuals who will To detect individuals who will benefit from early diagnosis benefit from early diagnosis and treatment, thus reducing and treatment, thus reducing morbidity and mortalitymorbidity and mortality

Cascade family screeningCascade family screening

To target at risk families and To target at risk families and offer future genetic choiceoffer future genetic choice

To allow better Health Service To allow better Health Service resource planningresource planning

ANTENATALANTENATALTo target at risk couples and To target at risk couples and offer genetic choiceoffer genetic choice

To offer family screeningTo offer family screening

To detect individuals with To detect individuals with sickle cell syndromes who will sickle cell syndromes who will benefit from diagnosis and benefit from diagnosis and treatment, thus reducing treatment, thus reducing morbidity and mortalitymorbidity and mortality

Antenatal and neonatal

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The aim of the programme is to detect The aim of the programme is to detect the following:the following:

NEONATALNEONATAL

SSSS

SCSC

SDSD

SO-ARABSO-ARAB

SBETASBETA

ANTENATALANTENATAL

SS

C C

D-PunjabD-Punjab

E E

O-ArabO-Arab

Beta thal traitBeta thal trait

Delta/beta thal traitDelta/beta thal trait

AlphaAlpha00 thal trait thal trait

LeporeLepore

Antenatal and neonatal

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Neonatal Screening Programme - Neonatal Screening Programme - EnglandEngland

UUniversalniversal

UUse dried blood spotsse dried blood spots

CContemporaneously with PKU and Thyroidontemporaneously with PKU and Thyroid

FFirst line screen to be either HPLC or IEF irst line screen to be either HPLC or IEF

SSecond line confirmation to be either IEF or HPLCecond line confirmation to be either IEF or HPLC

Neonatal

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Beta thalassaemia traitBeta thalassaemia trait

Some cases of beta thalassaemia intermediaSome cases of beta thalassaemia intermedia

Some rare variantsSome rare variants

HPFHHPFH

What we cannot detect with Neonatal What we cannot detect with Neonatal ScreeningScreening

Neonatal

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Antenatal Screening Programme - Antenatal Screening Programme - EnglandEngland

Areas are defined as high or low Areas are defined as high or low prevalenceprevalence

High prevalence is defined as a foetal High prevalence is defined as a foetal prevalence rate for sickle cell disease of prevalence rate for sickle cell disease of 1.5 or more per 10000 pregnancies1.5 or more per 10000 pregnancies

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Testing regimes for high and low prevalence Testing regimes for high and low prevalence areasareas

High prevalenceHigh prevalence

All samples tested for All samples tested for thalassaemia and Hb variants by thalassaemia and Hb variants by laboratory methodslaboratory methods

Family origin question used to Family origin question used to assess the need for partner assess the need for partner testing in cases of possible alphatesting in cases of possible alpha00 thalassaemiathalassaemia

Low prevalenceLow prevalence

All samples screened for All samples screened for thalassaemia using red cell thalassaemia using red cell indicesindices

All women assessed for All women assessed for laboratory testing for variants laboratory testing for variants by use of the family origin by use of the family origin questionquestion

Family origin question used to Family origin question used to assess the need for partner assess the need for partner testing in cases of possible testing in cases of possible alphaalpha00 thalassaemia thalassaemia

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Family Origin QuestionnaireFamily Origin Questionnaire

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Outline of the investigation scheme for haemoglobin Outline of the investigation scheme for haemoglobin disordersdisorders

FBC,HPLC/Electrophoresis

MCH,A2,F normal, No structural variant seen,

no evidence of erthyrocytosis or haemolytic anaemia.

Reduced MCH Variant detected

Probably normal, but a silent

mutation cannot be excluded

Raised Hb A2Normal/low A2,

raised FNormal A2 and F

IEF,Cellulose acetate,

Acid electrophoresis as appropriate.

Sickle test.

Beta Delta/beta Possible Fe def

Possible alpha thal

Rare cases of beta thal

Antenatal

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Outline of the investigation scheme for haemoglobin Outline of the investigation scheme for haemoglobin disordersdisorders

FBC and information from FOQ

MCH normal, No structural variant seen,

or test not indicated by FOQ no evidence of erthyrocytosis

or haemolytic anaemia.

Reduced MCHHPLC/Electrophoresis

indicated by FOQ

Probably normal, but a silent

mutation cannot be excluded

Raised Hb A2Normal/low A2,

raised FNormal A2 and F

IEF,Cellulose acetate,

Acid electrophoresis as appropriate.

Sickle test.

Beta Delta/beta Possible Fe def

Possible alpha thal

Rare cases of beta thal

HPLC/Electrophoresis Variant detected

Antenatal

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Risk assessment of using the algorithmRisk assessment of using the algorithm‘‘Silent’ or ‘near silent’ Silent’ or ‘near silent’ -thalassaemia trait-thalassaemia traitPossibly some Possibly some -thalassaemias obscured by severe -thalassaemias obscured by severe iron deficiency anaemiairon deficiency anaemia00thalassaemia occurring outside the defined at risk thalassaemia occurring outside the defined at risk groupsgroupsDominant haemoglobinopathies in the partner when Dominant haemoglobinopathies in the partner when the woman is AA, - very rare and should be suggested the woman is AA, - very rare and should be suggested by the family history by the family history Some women may not be tested if the ethnic group is Some women may not be tested if the ethnic group is incorrectly stated or hidden.incorrectly stated or hidden.-thalassaemia obscured by B12/folate deficiency or -thalassaemia obscured by B12/folate deficiency or liver diseaseliver diseaseHb S, C, DHb S, C, DPunjabPunjab, E, O, E, OArabArab in the North-European ethnic in the North-European ethnic groupgroup

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Challenges - GeneralChallenges - General

What should we report?What should we report?

How should we report it?How should we report it?

How should we report it if we don’t know How should we report it if we don’t know exactly what it is?exactly what it is?

How should we convey what we can’t How should we convey what we can’t detect?detect?

All screening

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Challenges - NeonatalChallenges - Neonatal

Transfused babiesTransfused babies

Premature babiesPremature babies

Older babies/ Old samplesOlder babies/ Old samples

Gamma chain variantsGamma chain variants

Variants on HPLC and not IEF Variants on HPLC and not IEF

Variants on IEF and not on HPLCVariants on IEF and not on HPLC

Conflicts between child’s result and parental Conflicts between child’s result and parental resultsresults

Neonatal

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Challenges - AntenatalChallenges - Antenatal

A2 variantsA2 variants

Alpha/beta interactionsAlpha/beta interactions

Silent beta thalassaemia traitSilent beta thalassaemia trait

Alpha thalassaemia Alpha thalassaemia

B12/Folate/Iron deficiencyB12/Folate/Iron deficiency

Borderline raised A2 valuesBorderline raised A2 values HIVHIV SporadicSporadic

Antenatal

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What we aim to provideWhat we aim to provide

Agreed turnaround timesAgreed turnaround times

Readable reports with explanations and Readable reports with explanations and recommended actionsrecommended actions

Advice if neededAdvice if needed

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Report elements (Antenatal)Report elements (Antenatal)

The numeric dataThe numeric data FBC (Hb,MCV and MCH)FBC (Hb,MCV and MCH) The A2The A2 Any Variants foundAny Variants found

• Interpretation of the resultsInterpretation of the results

• The action recommendedThe action recommended

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What we expect to receiveWhat we expect to receive

Properly labelled samples and legible Properly labelled samples and legible formsforms

Partners correctly identifiedPartners correctly identified

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LINKAGE – the final frontierLINKAGE – the final frontier

The antenatal and neonatal screening in The antenatal and neonatal screening in England are intended to be linked programmesEngland are intended to be linked programmes

For each baby, the antenatal results should be For each baby, the antenatal results should be available at the time of the neonatal screen. available at the time of the neonatal screen.

The neonatal result should be used to The neonatal result should be used to crosscheck that each couple had the appropriate crosscheck that each couple had the appropriate antenatal screening offered and carried out.antenatal screening offered and carried out.