Does Timing of Urine Sample Affect Pregnancy Test Accuracy?

Will the accuracy of a pregnancy test be affected if there is a time interval between sample collection?

Hello doctor, I had negative pregnancy test results on days 21 and 25 after my last sexual intercourse.
My most recent test involved collecting morning urine for about 5 seconds, then waiting approximately 30 seconds before collecting another 5 seconds.
Is there a difference between this method and collecting for 10 seconds at once? I'm concerned that the concentration might not be sufficient for an accurate result.
Is this result reliable? Thank you, doctor.

Ms. Chen, 20~29 year old female. Ask Date: 2023/05/04

Dr. Huang Yuande reply Obstetrics and Gynecology

1.
No difference.
2.
Please ensure interpretation is completed within 15 minutes.

Reply Date: 2023/05/04

More Info

The timing and method of urine sample collection can indeed affect the accuracy of a pregnancy test. Pregnancy tests work by detecting the hormone human chorionic gonadotropin (hCG), which is produced shortly after a fertilized egg attaches to the uterine lining. The concentration of hCG in urine increases as the pregnancy progresses, which is why the timing of the test and the method of urine collection are crucial for accurate results.

In your case, you mentioned that you collected a morning urine sample by first taking a sample for about 5 seconds, waiting for 30 seconds, and then taking another sample for another 5 seconds. This method of collecting urine may dilute the concentration of hCG in the sample, especially if the first sample was not concentrated enough. Generally, the best practice for urine pregnancy testing is to use the first morning urine, as it is usually the most concentrated and has the highest levels of hCG.

If you are concerned about the accuracy of your results, it is advisable to follow a more standardized method for urine collection. For instance, you could collect a single sample of first morning urine for at least 10 seconds, ensuring that the sample is concentrated. This method would likely provide a more reliable result.

Moreover, if you have already tested negative on two occasions (21 and 25 days after intercourse), it is possible that you are not pregnant, especially if you are using a reliable pregnancy test. However, if your menstrual period is still delayed and you have symptoms that could indicate pregnancy, it may be worth testing again. If you choose to retest, consider waiting a few days to allow for any potential increase in hCG levels, especially if you are testing early in the pregnancy.

In summary, the timing and method of urine sample collection can significantly impact the accuracy of a pregnancy test. For the most reliable results, use a concentrated first morning urine sample and follow the instructions provided with the test kit carefully. If you continue to have concerns or if your period does not arrive, consulting with a healthcare provider for further evaluation and possibly a blood test for hCG may be beneficial. Blood tests can detect lower levels of hCG and provide a more definitive answer regarding pregnancy status.

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