Page 421 - Handbook of Biomechatronics

416 Graham Brooker

The package insert describes the test principle and composition for these
strips, an example of which is the ACCU-CHEK Performa shown in
Table 1. Calibration codes are often included with each batch of strips,
and this must be entered manually in at-home testers. The more expensive
meters used in hospitals include a barcode that can be read by the meter to
facilitate automatic calibration.
User interaction has been simplified over the years to minimize the
potential for errors in the sampling and testing process. One of the main
problems was smearing a drop of blood on top of the strip, so modern strips
use capillary action to draw blood from the end of the strip onto the active
surface, as shown in Fig. 3. This small capillary space only requires about
300nL of blood. Lancets have become thinner and sharper and are available
in carrousels that are loaded into a pen-like device that automatically lances
and then retracts the point. This controls the insertion depth and minimizes
the pain from each finger prick while still providing sufficient blood for a
measurement.
Alternate sites provide capillary blood with slightly different glucose and
hematocrit values to the fingertip and need separate calibration. Because of
the larger volume available to provide a blood sample, some alternate site
testers extract blood by drawing a vacuum over a lanced site to increase
the width of the lancet wound opening as the skin is stretched.
3.3 Glucose Meter Hardware

The hardware and software functionality for a typical glucose meter is dis-
cussed in relation to Maxim and Microchip components (DiCristina, 2017;
Dalvi, 2013).

Table 1 Test Principle and Composition of the ACCU-CHEK Performa Strips