On a home pregnancy test, the letters ‘T’ and ‘C’ typically represent the test line and the control line, respectively. The ‘C’ line confirms the test is working correctly; its appearance indicates that sufficient fluid has passed through the test strip. The ‘T’ line indicates the presence of the pregnancy hormone human chorionic gonadotropin (hCG) in the urine. If hCG is present above a certain threshold, the ‘T’ line will appear, suggesting a positive result. For example, if both lines appear, even faintly, the test is usually considered positive, while the presence of only the ‘C’ line indicates a negative result.
The appearance of these lines is critical for accurate interpretation of the results. The control line assures the user that the testing process itself was successful, irrespective of whether the individual is pregnant. Without a visible control line, the test result is invalid and must be repeated with a new test. This binary system, using designated lines for control and indication, allows for a relatively simple and accessible method of early pregnancy detection from the privacy of one’s home. Its widespread availability has revolutionized early pregnancy detection, offering convenience and discretion.
