Biomedical Engineering Reference
In-Depth Information
Diagnosing Infections
Fast diagnosis of some infections is important to allow timely treat-
ment. Accurate and easy-to-use test kits allow clinic and emergency
room staff to identify or rule out an infection suspected because of
the patient's symptoms. For these tests, a small sample of blood or
other body fluid is put into cellulose-bottomed wells on the side
of a cigar-shaped plastic device, and tandem pairs of monoclonal
antibodies lock onto different parts of the infecting bacterium,
fungus, virus, or other infection, signaling the presence of the
pathogen. In a typical kit, one monoclonal antibody linked to a
gold-colored particle that traps the intended target, and the mixture
is wicked by the cellulose to a band or spot where the other antibody
is stuck. If the target of the two antibodies is present in the sample,
the spot or band will change color because the colored complex is
concentrated in a small area. Kits using this technology allow for a
quick diagnosis of influenza and malaria.
Other Diagnostic Uses
Hospital and commercial diagnostic testing laboratories rely on
monoclonal antibody tests to measure the amounts of specific proteins,
hormones, or drugs in blood. Monoclonal antibodies tagged to fluo-
rescent dyes are also used with lasers to determine the kind of tumor a
patient has, to track the number of tumor cells, and to monitor the level
of immune system cells. The CD4 count test, important to patients with
HIV infection, uses monoclonal antibodies and a laser-driven device
that checks cell by cell for the CD4 protein, the marker for the critical
immune system cell. The same technology and a set of antibodies to
immune system cell proteins are used to diagnose children suspected
of having inherited an immune system deficiency.
Home-based Tests
Test kits based on paired monoclonal antibodies are so reliable and
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