RDT test: design and function: Difference between revisions
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In a typical test the buffer containing lysing agents is loaded into one window ('''A'''), then the blood sample is loaded into a second window ('''B'''). The interaction between blood and buffer causes lysis of the blood sample and the relaesed proteins diffuse along the strip where they encounter lablelled antibody ('''Ab'''). After encountering the antibody the lysate continues to migrate along the strip driven by excess buffer ('''blue arrow''').</br> | |||
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This process is also shown in more detail below: buffer ('''A''') and blood sample ('''B''') enter the strip. The lysed red cells and any parasite antigens then encounter the labelled antibody ('''Ab'''). If malaria antigens are present they bind to the antibody to form labelled immune-complexes (as shown). | |||
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The lysed red cell preparation containing free-labelled antibody and any labelled-immune-complexes then continues to migrate along the strip (red arrow) pushed by the remianing buffer (blue arrow). If the test has been performed correctly the lysed red cells will reach the end of the strip, first passing over the test ('''T''') and control areas ('''C'''). | |||
Revision as of 22:54, 27 June 2024
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Test formats vary, but share common principles - this is illustrated using a test for a single P.falciparum parasite antigen below.
| TEST PROCESS |
In a typical test the buffer containing lysing agents is loaded into one window (A), then the blood sample is loaded into a second window (B). The interaction between blood and buffer causes lysis of the blood sample and the relaesed proteins diffuse along the strip where they encounter lablelled antibody (Ab). After encountering the antibody the lysate continues to migrate along the strip driven by excess buffer (blue arrow).
This process is also shown in more detail below: buffer (A) and blood sample (B) enter the strip. The lysed red cells and any parasite antigens then encounter the labelled antibody (Ab). If malaria antigens are present they bind to the antibody to form labelled immune-complexes (as shown).
The lysed red cell preparation containing free-labelled antibody and any labelled-immune-complexes then continues to migrate along the strip (red arrow) pushed by the remianing buffer (blue arrow). If the test has been performed correctly the lysed red cells will reach the end of the strip, first passing over the test (T) and control areas (C).
| PART 2: A "POSITIVE " test result |
This dye-labelled antigen/antibody complex then diffuses along the strip until it encounters a second parasite-specific antibody immobilised as a band on the strip. This immobilised antibody “captures” the labelled antibody/antigen complex to form a visible line (capture 1 = C). The remaining lysed sample (containing labelled antibody not bound to parasite antigen) continues to diffuse along the strip. And encounters a further immobilised antibody that captures it. This forms a control line which indicates that test has been successfully performed (capture 2 = D).
(2) Where the parasite-antigen is present, the dye-labelled antibody will bind to that antigen to form a complex (binding=B). This dye-labelled antigen/antibody complex then diffuses along the strip until it encounters a second parasite-specific antibody immobilised as a band on the strip. This immobilised antibody “captures” the labelled antibody/antigen complex to form a visible line (capture 1 = C).
(3) The remaining lysed sample (containing labelled antibody not bound to parasite antigen) continues to diffuse along the strip. And encounters a further immobilised antibody that captures it. This forms a control line which indicates that test has been successfully performed (capture 2 = D).