PROCEDURE MANUAL FOR THE i-STAT SYSTEM
29
REV. DATE: 16-Oct-12 ART: 714446-00L
Troponin I/cTnI
is determined amperometrically using a two-site ELISA method. Antibodies specific for human cardiac troponin I
(cTnI) are located on an electrochemical sensor fabricated on a silicon chip. Also deposited in another location on the
sensor silicon chip is an antibody/alkaline phosphatase enzyme conjugate specific to a separate portion of the cTnI
molecule. The whole blood or plasma sample is brought into contact with the sensors allowing the enzyme conjugate to
dissolve into the sample. The cTnI within the sample becomes labeled with alkaline phosphatase and is captured onto
the surface of the electrochemical sensor during an incubation period of approximately seven minutes. The sample, as
well as excess enzyme conjugate, is washed off the sensors. Within the wash fluid is a substrate for the alkaline
phosphatase enzyme. The enzyme bound to the antibody/antigen/antibody sandwich cleaves the substrate releasing an
electrochemically detectable product. The electrochemical (amperometric) sensor measures this enzyme product which
is proportional to the concentration of cTnI within the sample.
Creatine Kinase MB/CK-MB
is determined amperometrically using a two-site ELISA method. Antibodies specific for an epitope unique to the
CK-MB subunit, that therefore do not bind CK-MM or CK-BB, are located on an electrochemical sensor fabricated on a
silicon chip. Also deposited in another location on the sensor silicon chip is an antibody/alkaline phosphatase enzyme
conjugate specific to an epitope on the B subunit of creatine kinase. The specificity of the conjugate antibody to the B
subunit allows this conjugate to recognize CK-MB and CK-BB, but not CK-MM. The whole blood or plasma sample is
brought into contact with the sensors allowing the enzyme conjugate to dissolve into the sample. The CK-MB within
the sample becomes labeled with alkaline phosphatase and is captured onto the surface of the electrochemical sensor
during an incubation period of approximately three minutes. The sample is washed off the sensors, as well as excess
enzyme conjugate. Within the wash fluid is a substrate for the alkaline phosphatase enzyme. The enzyme bound to the
antibody/antigen/antibody sandwich cleaves the substrate releasing an electrochemically detectable product. The
electrochemical (amperometric) sensor measures this enzyme product which is proportional to the concentration of
CK-MB within the sample.
B-Type Natriuretic Peptide/BNP
i
s determined amperometrically using a two-site ELISA method. Antibodies specific for BNP are located on an
electrochemical sensor fabricated on a silicon chip. Also deposited in another location on the sensor silicon chip is an
antibody/alkaline phosphatase enzyme conjugate specific to a separate portion of the BNP molecule. The whole blood
or plasma sample is brought into contact with the sensors allowing the enzyme conjugate to dissolve into the sample.
The BNP within the sample becomes labeled with alkaline phosphatase and is captured onto the surface of the
electrochemical sensor during an incubation period of approximately seven minutes. The sample is washed off the
sensors, as well as excess enzyme conjugate. Within the wash fluid is a substrate for the alkaline phosphatase enzyme.
The enzyme bound to the antibody/antigen/antibody sandwich cleaves the substrate releasing an electrochemically
detectable product. The electrochemical (amperometric) sensor measures this enzyme product which is proportional to
the concentration of BNP within the sample.
TCO
2
The measured TCO
2
test method is calibrated to the International Federation of Clinical Chemistry (IFCC) TCO
2
reference method with an algorithm, based on the Henderson-Hasselbach equation, which uses pH, PCO
2
, and ionic
strength (Na) measurements.
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