ple allergens can be detected simultaneously in a
sample. The advantages of
these types of assays are
their very short analysis
time (seconds), simultaneous detection of multiple
allergens, small sample volume and relatively low-priced machines (compared
with biosensors). However,
labor times are comparable
to those of ELISAs.
Figure 4: Principle of a microsphere-based flow cytometric
assay: Differently colored beads are coated with antibodies
Selecting a
against different allergens. Fluorescently labeled second anti-
Detection Method
bodies are used to visualize binding of allergens to the beads. When selecting a
Multiple allergens can be detected simultaneously.
suitable detection method,
labeled, second antibodies are used to the following criteria should be consid-visualize the binding of allergens to the ered: availability of laboratory personnel
beads. For analysis, different bead sets and standard laboratory equipment,
(to detect different allergens) are added number of samples, number of allergens
simultaneously to a sample in a mi- to be detected, frequency of testing,
crotiter well. The beads are drawn up need for short analysis time, need for
into a fluidic tube that causes the mi- quantitative results, ease of use, degree
crospheres to line up in single file before of automation and the resulting costs. In
they pass through the detection cham- Figure 5, a simplified selection scheme is
ber. In this chamber, one laser identifies presented.
each bead and categorizes it into the ap- When a company doesn’t have
propriate bead set (based on which aller- trained lab personnel or equipment, the
gen is detected), while another laser only tests that employees can perform
scans the beads for the quantity of fluo- by themselves are strip tests. When a
rescently labeled antibodies per bead high number of samples are required to
(and determines the concentration of be analyzed for only a single allergen,
the detected allergen). In this way, multi- (continued on page 53)
Figure 5. Scheme for Selecting a Suitable Immunoassay
