Anon-extractionassaywith
highspecificity

Themeasurementofinsulin-likegrowthfactor-I(IGF-I)inserumisofespeciallyhighutilityinthediagnosticwork-upofgrowthdisturbances,particularlywithregardtohumangrowthhormone(hGH)deficiencyoracromegaly.ThemostimportantadvantageofmeasuringIGF-IoverhGHareitsstablecircADIanlevels,i.e.evenasinglemeasurementisofconclusivesignificance.

Inviewoftheabove,measurementofIGF-Ishouldbeputonthefrontburnerinlaboratorydiagnosticwork-up.

TheadvantagesofourELISAsare:

• non-extractionassay;
• highspecificityforIGF-I;
• nointerferencefromIGF-bindingproteins(IGFBP);
• onlyasamplevolumeof10µLrequired;
• onesampledilutionsuffices(usually1:21);
• calibratedagainsttheinternationalstandardofWHONIBSC02/254;
• veryhighsensitivity(0.09ng/mL);
• outstandingaccuracy--98.7%recovery;
• remarkableprecision:inter-assayvarianceof6.8%andintra-assayvarianceof6.7%.

IBLInternational´sIGF-Ienzymelinkedimmunosorbentassay(ELISA)byIBLInternationalisusedformeasuringIGF-Iinhumanserum/plasma,cerebrospinalfluidandotherbodyfluidsaswellasinconditionedcellculturemediaofmanyhumancelllines.

Whatismore,theassaycanalsobeusedforthemeasurementofIGF-Iinothermammalssuchasprimates,cattle,pig,sheep,horse,donkey,goat,dog,cat,rabbitandguineapig.However,thekitisnotsuitedforrat,mouseandchickensamples

Insulin-likegrowthfactorsIandII(IGF-I,IGF-II)playakeyroleinproliferation,differentiationandspecificfunctionsofmanycelltypes.IGF-IisidenticaltosomatomedinC(Sm-C)andisregulatedbythegrowthhormone(hGH/GH)andnutrition.Unlikemanyotherpeptidehormones,IGFsareboundtospecificbindingproteins(IGFBP)withahighaffinity.AsubstantialprobleminthemeasurementofIGF-IlevelsistheinterferencebyIGFBPs.Whenmeasuredinuntreatedserumsamples,inaccurateresultsareobtainedduetotheextremelyslowdissociationoftheIGF-I/IGFBP-3complexduringassayincubation.Forthisreason,onlyafractionofIGF-Iisavailableformeasurement.InterferencesaredeterminedbytheIGF-ItoIGFBPratiointhesample.

Inordertocircumventthisproblem,asimpleassaywasdevelopedinwhichsamplesareacidifiedanddilutedusingabufferofaspecialcompositionpriortoperformingELISA.

ClinicalSignificance

ApartfromhGH,anumberofotherfactorsaffectserumIGF-Ilevels.Lowvaluesarefoundinmalnutrition/malabsorption,hypothyroidism,liverdisease,untreateddiabetesmellitus,chronicinflammatorydiseases,malignanciesandmultipletrauma.Elevatedlevels,ontheotherhand,arefoundinprecociouspubertyandobesity.

InordertobeabletocorrectlyinterpretIGFmeasurements,itisofutmostimportancetoconsidertheage-dependentpatternofIGF-1levels,whichyoucanfindintheInstructionforUse.

Percentiles
Pubertätsstadium	0.1th	5th	50th	95th	PubertalStage
1	61	105	186	330	1
2	85	156	298	568	2
3	113	196	352	631	3
4	171	268	431	693	4
5	165	263	431	706	5

ForconcretedatapleaseconsulttheInstructionforUseinthedownloadboxontherightside.