05
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 to 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
increases, which results into a change in blood flow behaviour.
The Meter captures the position of the sample by means of a
Machine vision system and the position is transformed
mathematically into speed and acceleration curves, from
which an INR value is obtained.
Calibration
Each batch of microINR Chips has been calibrated against a
reference batch of human recombinant thromboplastin traced
to International Reference Thromboplastin of the World Health
Organization
1
.
These calibration values (ISI and MNPT) are encoded in the
printed Datamatrix of each microINR Chip. Therefore, every
test is automatically and individually calibrated eliminating
any risk of human error.
(1). Expert committee of the WHO on biological normalization.
Report forty-eight. Geneva, World Health Organization, 1999
(WHO technical report series No. 889)
ENTRY CHANNEL
MICROREACTORS
DATAMATRIX
MICROCAPILLARY
CHANNELS
CONTROL CHANNEL MEASURING
CHANNEL
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