Helena C-4 - Atest/Marketing

Operation Manual
Helena C-4 - Software C11.11b
Helena Biosciences Europe
UK
Chromogenic Assay (KINETIC)
In this method, the end result is determined from the rate of optical density change. Test
plasma is pre-incubated with an enzyme (i.e. – Factor Xa for determination of AT-III) and
residual enzymatic activity is detected by the addition of a chromogenic substrate. The
concentration of the analyte in the test plasma is directly or indirectly proportional
(depending on the reagent system) to the rate of substrate hydrolysis, and is reported as
the mean slope of optical density per minute (delta OD(E)/min).
EXTINCTION
1.000
E2
100mOD
E1
0
t1
t3
t2
end of
test
time in sec
Chromogenic Assay
result = slope of curve per minute
result = (E2 - E1)/(t2 - t1) if t2 - t1 = 1 min
Chromogenic Ecarin Assay
result = t3
Figure 6 - The chromogenic method
4.4 Chromogenic Ecarin Assay (100mOD)
The measurement principle is similar to a regular chromogenic assays. But the result is the
time between start of test and when signal brake through 100mOD.
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