2. Describe other methods for CK-MB assays.Two-tube
immunochemical methodAnewcommercial kit (Impres-MB; International
ImmunoassayLabs.)recentlywasintroducedormeasurin!theMBisoen"yme o
creatine kinase (#$-MB) based on the use o monoclonal antibodies.
Ater antibodies to #$-MM isoen"ymeare added to precipitate the
#$-MM% antibodies to #$-M monomer are added to precipitate the
M-subunit isoen"ymes o#$. &ubtractin! the en"ymatic acti'ity o
the second supernate rom the residual acti'ity in the irst yields
the acti'ity o#$-MB. (esults are not aected by #$-BB% mitochondrial
#$% or adenylate kinase. )owe'er% the anti-#$-MM
antibodiesprecipitated only about *+, o serum #$-MM and may ha'e
partly precipitated #$-MB isoen"yme (a'era!e analyticalreco'ery
o#$-MB% +-.-,).#omparison between Impres-MB(y)and
electrophoresis(.) yieldedtheollowin!linear-re!ression e/uation0 y
1 2.3*. 4 5 (r 1 2.*+6% n 1 *3). 7ata or #$-MB temporal kinetics%
obtained rom patients withmyocardial inarction% correlated
si!niicantly in both methods; howe'er% peak acti'ity 'alues o #$-MB
were si!niicantlydierent% conirmin! that the dierence between the
new method and the electrophoretic method a'era!e 62,. i-STAT CK-MB
testThe i-&TAT #$-MB test is an in 'itro dia!nostic test or the
/uantitati'e measurement o creatine kinase MB mass in
wholebloodorplasmasamples.
#$-MBmeasurementscanbeusedasanaidinthedia!nosisandtreatmentomyocardialinarction
(MI). The i-&TAT #$-MB test cartrid!e uses a two-site
en"yme-linked immunosorbant assay (8LI&A) method.Antibodies
speciic or an epitope uni/ue to the #$-MB subunit% that thereore do
not bind #$-MM or#$-BB% are locatedon an electrochemical sensor
abricated on a silicon chip.Also deposited in anotherlocation on
the sensor silicon chip is anantibody9alkaline phosphatase en"yme
con:u!ate speciic to an epitope on the B subunit o creatine kinase.
The speciicityo the con:u!ate antibody to the B subunitallows this
con:u!ate to reco!ni"e #$-MB and #$-BB% but not #$-MM.Thewhole
blood or plasmasample is brou!ht into contact with the sensors
allowin! the en"yme con:u!ate to dissol'e into thesample.The #$-MB
within the sample becomes labeled with alkaline phosphatase and is
captured ontothe surace o theelectrochemical sensor durin! an
incubation period o appro.imately three minutes. The sample is
washed o the sensors%as well as e.cess en"yme con:u!ate.;ithin the
wash luid is asubstrate or the alkaline phosphatase en"yme.The
en"ymebound to the antibody9anti!en9antibody sandwich clea'es the
substrate releasin! an electrochemically detectable product.The
electrochemical (amperometric) sensor measures this en"yme product
which is proportional to the concentration o#$MB within the
sampleWuerzburg et al. ad !erhardt et al. Method;hile these
procedures can be useul% newer methods ha'e recently been
introduced by ;uer"bur! et al. and in the presence o creatine
phosphate to orm AT> andcreatine. The au.iliary en"yme
he.okinase ()$) cataly"es the phosphorylation o !lucose by the
AT> ormed% to produceA7> and !lucose---phosphate ().The is
o.idi"ed to --phospho!luconate with the concomitant production
o@A7).The rate o @A7) ormation% measured at 5A2nm% is
directlyproportional to serum #$-B acti'ity."mmuoihibitio#$-MB is
composed o the two moieties #$-M and #$-B. A speciic antibody
inhibits the #$-M moiety. This antibody will bind to and inhibit
the acti'ity o the M subunit o #$-MB. This means that only the
acti'ity o the B subunit in serum is measured by the @A#-acti'ated
creatine kinase reaction. I the acti'ity is multiplied by a actor o
6% it will !i'e the acti'ity o #$MB in serum.Atypical macro #$ may
result in alsely ele'ated #$-MB results. =or this reason% this
assay is primarily used as a screenin!test to eliminate ne!ati'e
#$-MBBs% and all positi'e #$-MBBs by immunoinhibition are urther
in'esti!ated.Mass measuremet The mass assay or #$-MB is an
immunometric sandwich assay. 8ither a polyclonal% or more widely
used today% monoclonal antibody is linked to the #$-MB moiety% the
#$-MM or the #$-BB is also co'alently linked to a poly or
monoclonal antibody bound to a solid surace or parama!netic
particles% then eluted by a series o washes% and inally% #$-MB is
measured throu!h production o luoro!enic substrate (e.!.
&tratus% 7ade 7i'ision% IMC% Abbott Laboratories) or usin!
chemiluminescence (A#&0D+2E% #iba #ornin!).
#$%$#$&C$'http099www.chronolab.com9point-o-care9inde..phpFoption1comGcontentH'iew1articleHid1AD+HItemid1-3
http099www.ncbi.nlm.nih.!o'9pubmed96D3++25
http099www.i-stat.com9products9ctisheets93D--3I-22
