Page 416 - Handbook of Biomechatronics

The Artificial Pancreas 411

A trial consisting of 34 volunteers compared the performance of this
technique with a reference Technicon AutoAnalyzer. Blood was drawn
from the antecubital vein, allowed to clot and the serum removed for
processing in the AutoAnalyzer while simultaneously finger-prick blood
was applied directly to the strip, allowed to react for 60s before the strip
was washed and the color measured using the reflectance meter. These tests
provided the first confirmation that the technique was sound, as can be seen
from a comparison graph shown in Fig. 1, though slight differences between
the values measured by the two techniques were noted at low and high glu-
cose concentrations (Mazaferri et al., 1970).
Optically based strips are generally made up of various layers, each of
which provides a specific function: support, reflective, analytical, and sample
spreading, as illustrated in Fig. 2. The support function provides a founda-
tion for the dry reagent and may also include the reflective material. Oth-
erwise scattering or reflective components including TiO 2 , BaSO 4 , MgO,
or ZnO, are added to the dry reagent. The analytical layer contains the active
enzyme, while the spreading function must rapidly disperse the blood to
cover the active layer as uniformly as possible. These have been made from

Fig. 1 Comparison between the blood glucose levels measured by an AutoAnalyzer and
a Color Reflectance Meter. (Data from Mazaferri, E., Skillman, T., Lanese, R., Keller, M., 1970.
Use of test strips with colour meter to measure blood glucose. Lancet 265(7642): 331–333.)