THE
SCIENCE
Of The Test Strip
“Just How Do These Things
Work Anyway?”
Absorbent Pad
Ensures proper wicking of the sample.
Control “C” Line
The control line indicates the integrity of the test. If no control line
appears on the test, an invalid test is indicated. If this occurs, run
a second test.
Nitrocellulose Membrane
Nitrocellulose is widely used as support in diagnostic tests where
antigen-antibody binding occurs - making protein transfer more efficient.
Target Drug Conjugate
on Test or “T” line
Label Pad
Test “T” Line
The label pad contains two species of antibody types - one for the
drug target, one for the control. When the sample wets the label
pad it releases the antibodies allowing them to wick up the test
strip with the specimen.
Any colloidal gold-labeled antibody particle not already bound to drug
molecules can adhere to the immobilized drug conjugate striped at the
test line region. If there’s no target drug at or above the stated cut-off
level, a colored line will form as a result of the antibody-antigen binding.
Antibodies coated with
colloidal gold in label pad
Any drug present in the specimen, binds to the drug antibody.
Conjugate Tape
Sample Pad
Ensures the Label Pad and Sample Pad are bound together.
When the urine or saliva specimen comes in contact
with the sample pad, it starts wicking upward via capillary
movement until it moves into the label pad.
Target Drug In
Urine or Saliva
Reading
The
Results
Negative?
Positive?
Invalid?
(C) Control Line
(T) Test Line
(C) Control Line
(T) Test Line
(C) Control Line
(T) Test Line
Negative
A negative result is indicated by the presence of the lower “Test” or “T” Line
for each designated drug.
The presence of even a very light “Test” or “T” Line indicates a negative result.
Positive
A positive result is indicated by the absence of the lower “Test” or “T” Line
for a specific drug. Wait 5 minutes to determine a positive result.
Invalid
(C) Control Line
(T) Test Line
(C) Control Line
(T) Test Line
An invalid result is indicated by the absence of the upper “Control” or “C” Line
and the lower “Test” or “T” Line for a specific drug.
An invalid result is also indicated by the absence of the upper “Control” or “C” Line
and the presence of the lower “Test” or “T” Line for a specific drug.
If either of these occurs, run a second test.
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