1.4 MEASURING PRINCIPLE
The technology used by the microINR system is based on the
microfluidics of the microINR Chip, which allows storing,
dosing, moving and/or mixing small volumes of liquids to
perform a chemical reaction.
The microINR Chips contain two channels, one for
measurement and the other for control. An image of the Chip
is shown below:
Each channel consists of a micro-reactor that contains the
reagent and a microcapillary where the INR is determined. The
reagent used in the measuring channel contains human
recombinant thromboplastin and the reagent in the control
channel contains recombinant thromboplastin and human
coagulation factors to normalize the patient’s blood.
The blood is applied on the Chip through the entry channel,
separated into two channels and mixed with the reagents
contained in each micro-reactor. The coagulation cascade is
triggered instantly. When blood coagulates, its viscosity
04
takes for a fibrin clot to form. Thromboplastin is used as a
reagent to calculate the prothrombin time (PT). Depending on
the nature of this reagent and the equipment used variations
on the PT results are to be expected.
Therefore, the WHO recommended a system standardisation
method in 1977. Prothrombin time values are converted into
INR values, International Normalized Ratio, using the following
equation:
Where PT is the prothrombin time obtained in the test, MNPT
is the mean normal prothrombin time and ISI the international
sensitivity index corresponding to the thromboplastin. The
values of the MNPT and ISI parameters come from clinical
calibration studies.
The pharmacological activity of vitamin K-antagonist
oral anticoagulants can be modified by other drugs;
therefore, you should only take the medicines
prescribed by your physician.
Certain liver diseases, thyroid disorders and other
diseases or conditions, as well as nutritional
supplements, medicinal herbs or changes in diets can
affect the therapeutic activity of oral anticoagulants
and INR results.
INR =
PT
ISI
MNPT
( )
ENTRY CHANNEL
MICROREACTORS
DATAMATRIX
MICROCAPILLARY
CHANNELS
CONTROL CHANNEL MEASURING
CHANNEL
To Next Page
Loading...
Need help?
General
