Short Answer
Complete Explanation
A home pregnancy test contains two important visual markers: the control line, marked with the letter “C,” and the test line, marked with the letter “T.” The control line appears on every test that has functioned correctly; it does not indicate pregnancy. Its presence confirms that the sample has moved through the test strip and that the reagents are active. If the “C” line fails to appear, the result is invalid and the test should be repeated with a new device.
- Control line (C):
Shows that the test has worked properly. It appears whether or not hCG (the pregnancy hormone) is present. - Test line (T):
If a second line appears at the “T” position, it indicates that hCG has been detected, suggesting pregnancy. - Result interpretation:
A valid result always includes a visible “C” line. One line (C only) means negative; two lines (C and T) mean positive. Faint lines may still be significant and should be read according to the manufacturer’s instructions.
Common Misconceptions
The “C” line means a positive result.
The “C” line only confirms that the test worked; a positive result requires a visible “T” line as well.
If the “C” line is faint, the test is unreliable.
A faint “C” line can still be valid; manufacturers specify the minimum intensity required for a valid control.
Absence of a “C” line means you are not pregnant.
No “C” line indicates an invalid test, not a negative pregnancy result.
FAQ
What does it mean if only the C line appears?
Only the C line means the test worked but did not detect hCG, indicating a negative result.
Can a faint T line still be a positive result?
Yes. Many manufacturers state that any visible T line, even faint, should be considered positive, but users should follow the specific test’s instructions.
What should I do if the C line does not appear?
An absent C line indicates an invalid test. Repeat the test with a new kit and ensure you follow the sample collection and timing instructions.
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