June 8th 2015
Immunology Laboratory
The Churchill Hospital
Old Rd
Headington
Oxford
OX3 7 LJ
Tel: 01865 225983
Fax: 01865 225990
Email: Berne.Ferry@ouh.nhs.uk
Web site : ouh.nhs.uk/immunology
Dear Colleagues,
Re: ChangingoftechniqueforthemeasurementofIgGsubclasses
Aspartoftheimplementationofchangefollowingtherecentre‐procurementprocessattheOUHTrust,
themethodcurrentlyusedinImmunologytomeasureIgGsubclasslevelsisabouttochange.
FromJune10th 2015wewillbeusingtheSPA+turbidimetersuppliedbyTheBindingSiteandusingThe
BindingSiteassaykit.PreviouslyweusedaBNIInephelometer,suppliedbySiemensandusingthe
Siemenskit.
VerificationofthisnewkithasbeencarriedbythelaboratoryaccordingtothestandardsoutlinedinISO
standard15189fordiagnosticlaboratories. Thishasincludedverifyingthereferencerangesquotedby
thecompanyforIgG1‐IgG4. Thenewadultreferenceintervalsthataretobeimplementedaredisplayed
below.
Adult
IgG1=3.80–9.30g/L
IgG2=2.40–7.00g/L
IgG3=0.20–1.80g/L
IgG4=0.04–0.86g/L
ThebiggestdifferenceseenbetweenpreviousandnewreferenceintervalsisseenwiththeIgG4level.
Thisdifferenceisexplainedbythefactthatthesuppliersusedifferentinternationalstandardstocalibrate
theirassays(TheBindingSiteusesCRM470,SiemensusesWHO67/97).
Thismeansthatallsamplescomparedwiththetwokitswillgivesignificantlydifferentresults
withbothvaluesgeneratedbeingequallytrue.
Below,wesummarisetheconsistencyofdifferencesbetweenthetwokitsandthenprovidesubclass
rangesoverdifferentagegroups.Wehopethatthischangewillcauseminimumdisruptiontoyourclinical
work.Pleasedonothesitatetocontactmeifyouhaveanyqueries
Yours sincerely
Professor BL Ferry
IgG4
Inordertoascertaintheconsistencyofdifferencebetweenthetwokits,arangeofsampleswererunon
bothassays. TheaveragebiasforIgG4onanysampleabove1g/LasmeasuredbythecurrentSiemens
techniqueis2.2whencomparedtoaresultthatwouldbegeneratedonthesamesampleusingthenew
BindingSitekit. Anexampleofthisisshownbelow:
Siemenskitresult 30g/L
÷2.2=
NewBindingSitekitresult
13.6g/L
IgG3
LevelsofIgG3arealsoseentobedifferentbetweenthetwokits;thebiasforthisanalytehasbeen
calculatedtobe0.6. Anexampleofthisisshownbelow:
Siemenskitresult 4g/L
÷0.6=
TheBindingSitekitresult
6.67g/L
IgGsubclassesreferenceintervals
0‐2yrs
IgG1‐1.94‐8.42
IgG2‐0.23‐3.00
IgG3‐0.19‐0.85
IgG4‐0.01‐0.78
2‐4yrs
IgG1‐3.15‐9.45
IgG2‐0.36‐2.25
IgG3‐0.17‐0.68
IgG4‐0.01‐0.54
4‐6yrs
IgG1‐3.06‐9.45
IgG2‐0.61‐3.45
IgG3‐0.10‐1.22
IgG4‐0.02‐1.13
6‐8yrs
IgG1‐2.88‐9.18
IgG2‐0.44‐3.75
IgG3‐0.16‐0.85
IgG4‐0.01‐0.99
8‐10yrs
IgG1‐4.32‐10.20
IgG2‐0.72‐4.30
IgG3‐0.13‐0.85
IgG4‐0.02‐0.93
10‐12yrs
IgG1‐4.23‐10.60
IgG2‐0.76‐3.55
IgG3‐0.17‐1.73
IgG4‐0.02‐1.15
12‐14yrs
IgG1‐3.42‐11.50
IgG2‐1.00‐4.55
IgG3‐0.28‐1.25
IgG4‐0.04‐1.36
14‐18yrs
IgG1‐3.15‐8.55
IgG2‐0.64‐4.95
IgG3‐0.23‐1.96
IgG4‐0.11‐1.57
Adults
IgG1‐3.82‐9.29
IgG2‐2.42‐7.00
IgG3‐0.22‐1.76
IgG4‐0.04‐0.86