RDT test: design and function

---

Navigation
Go back

---

Test formats vary, but share common principles - this is illustrated for a single parasite antigen below.

PART 1: Blood lysis and binding to labelled antibody

(1) In a typical test lysis buffer is loaded into one window (A), then the blood sample in a second window (B). Following this the lysed blood sample diffuses along the strip encontering lablelled antibody (Ab) then continues to diffuse into the window (pink arrow).

• 

• File:2 PF RDT lysate.jpg

(2) This process is shown below with buffer (A) and blood sample (B) entering the strip. The lysed red cells and any parasite antigens then encounter the labelled antibody (Ab). If malaria antigen is present it binds to the antibody to form immune complexes (shown in the window)."

• 

(3) The lysed red cell preparation then continues to migrate along the strip pushed by the remianing buffer (as shown by the arrow).

• 

---

PART 2: A "POSITIVE " test result

A positive test test result:

• 

• 

• 

• 

(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).