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Home pregnancy test offers definite results to women who want to confirm presence or absence of pregnancy. False negative urine pregnancy test causes include testing much earlier than suggested time, overweight, presence of low hCG levels, diluted urine, as well as in cases of expired pregnancy kits.
You have missed your cycles but still no BFP (Big Fat Positive). Confused as you are not feeling like every day and it’s different this time. You might be ‘expecting’ and be pregnant. There must be little spotting, swollen and tender breasts, food craving, backache and other early pregnancy symptoms which signals pregnancy. You are totally perplexed, as these are pregnancy symptoms or period’s symptoms. But you took a pregnancy test and it says negative. Is there a possibility of getting a false negative on the pregnancy test you took?
The answer to such confusion or question is ‘Yes, It can be’. There are several reasons for getting a false negative on your pregnancy test. But first, understand what home pregnancy tests are?
Home Pregnancy Test
Home Pregnancy test or Human Chorionic Gonadotropin (hCG) pregnancy test is the way to determine pregnancy by detecting hCG hormone in woman’s urine. Doctors suggest waiting for a week more, after you miss your menstrual cycle, for taking a home pregnancy test. If you don’t want to wait to find out and you are sure about the day you have conceived, in that case, you can take a test within 14 days from the possible conception. These home tests are 97% accurate when all the instructions are followed properly plus read the result in the stipulated time frame. Some of the kits have two tests for taking another pregnancy test if you have made a mistake in the first attempt. (1) (2)
What are the possible causes of getting a false negative pregnancy test?
There are several reasons for getting a false pregnancy test. And the most common cause of the false result is, missed reaction time. It is important for an individual to follow the directions mentioned on the kit, which clearly indicates the reaction time. The reaction time is the time required for the test to provide with the accurate result. Some of the pregnancy tests like EPT, Pregnancy Test takes about three minutes while other tests can take as long as four minutes to ten minutes. So, it is advised to go through the directions before starting the test, as it will help in preventing you from missing the reaction time. Taking the results before the reaction time or too late after the reaction time can result in a false-negative test result. (3) (4) (5)
Below is a quick rundown of the reasons behind getting a false negative pregnancy test:
1- Testing it too early
There are high chances of getting big fat negative (BFN) if you take a home pregnancy test too early even if you are already pregnant. This is one of the major reasons for getting negative results. The tests work by detecting the hCG presence in urine. After conception, the growing placenta secretes hCG once embryo implants into the uterus wall. It takes place after 7 to 10 days of ovulation. Though the hCG level increases rapidly initially as they double up in every 48-72 hours, the levels of hCG in very low around 6-8 dpo. Hence, testing before missing periods can result in false-negative on the pregnancy test. (6)
2- Test sensitivity too low
One should know that urine pregnancy test strips vary with its sensitivity. Home pregnancy test strips come in different shapes and sizes such as; test strips, midstream tests and digital tests. Some of the HPTs are sensitive to hCG and are made to detect even a low amount of hCG hormone-like 20mlU/ml. While other tests have low sensitivity to hCG and detect the higher amount of hCGsay 50 to 100 mlU/ml. (7)
Some women also get faint lines on pregnancy kits. Know the reasons for getting faint lines on a pregnancy test.
3- Urine too diluted
If you consume too much water or urinate frequently before taking tests then there are high chances that you lower down the hCG amount in urine. Try to test by using first-morning urine if you have got a negative result on the pregnancy test. First-morning urine is highly concentrated in hCG. It helps in finding out whether your earlier pregnancy test was actually false negative or not. Take a test again after a couple of days. Make sure to take a test in the morning by using a highly sensitive pregnancy test for the best result. (8)
4- Overweight and low hCG level
Women who have a high BMI have lower hCG hormone levels. It is also one of the reasons behind the false test results for pregnancy. (9)
5- The Hook Effect
The higher concentration of HCG can result in false-negative sometimes. This is called a hook effect. Hook effect can be confirmed by the positive pregnancy test after diluting the urine sample. The HCG array works by forming a sandwich where 2 different antibodies namely solid-phase antibody and labeled soluble antibody form a sandwich along with HCG molecule in between them. But the higher concentration of HCG saturates the antibodies; hence no sandwich is being formed. You get a false negative result in the absence of signal thus, resulting in ‘hook effect phenomenon’. (10)
The name has been suggested after observing the paradoxical decrease in curve plotting with increased antigen concentration appearing as a hook. Until and unless hCG concentration reaches up to 1,000,000 ml/ml, you cannot observe the hook in the urine hCG test. It is also seen in the gestational trophoblastic disease. Plus, the hook effect also results in false-negative results in normal pregnancies.
6- Improper Testing Technique:
Another common reason for a false negative pregnancy test result is the improper or erratic testing technique. Most of the test sticks need to be saturated in urine for getting accurate results. So, if you do not leave the test strip in the urine for a long duration as mentioned then there are chances of getting false negative or false positive pregnancy test results. Go through how to use a pregnancy test kit to make the most out of the home pregnancy kits.
7- Expired Pregnancy Kit:
Check the expiry date of the pregnancy test strip before purchasing. You cannot trust the results of the expired kit.
What to do when you get False Negative Results?
Depending upon the test result, you can consider the below steps:
- When your home pregnancy test is sometimes positive or sometimes negative after taking several tests, the best thing one can do is to consult the doctor. As he or she can determine clearly whether you are expecting or not through the blood test. The doctor will test by examining the blood sample. Blood pregnancy tests help in detecting the much lower levels of hCG. Thus, helps in getting better results and reduces the false-negative chances.
- When your home pregnancy test is negative and your menstrual cycle does not begin: It is advised to repeat the test. You can take another test in either few days or in one week. It is advised to take a test after missing your menstrual period.
- You keep getting negative test results and your period doesn’t begin but you still think you are expecting: Consult a doctor. There are several reasons for missing the menstrual cycle (amenorrhea) such as thyroid disorders, low body weight, ovaries problems, excessive stress, and heavy exercise.
Hope, this article helped you in understanding about the possible reasons for getting a pregnancy test false negative. For more information, you can also read about the Causes of False Positive Pregnancy Test
SOURCES AND REFERENCES:
- ^ Home Pregnancy Tests: How and When To Take Them | WebMD Webmd.com, 03 August 2019
- ^ How and When to Take a Pregnancy Test | Medical News Today Medicalnewstoday.com, 03 August 2019
- ^ Pregnancy Tests: Types and Results | Healthline Healthline.com, 03 August 2019
- ^ Pregnancy Test | Wikipedia En.wikipedia.org, 03 August 2019
- ^ When to Take a Pregnancy Test | Options, Cost and Accuracy Plannedparenthood.org, 03 August 2019
- ^ How Early Can Home Pregnancy Tests Show Positive Results? Utswmed.org, 03 August 2019
- ^ When Is the Best Time to Take a Pregnancy Test? | Verywell Family Verywellfamily.com, 03 August 2019
- ^ Diluted Urine Drug Tests | CleanFleet Cleanfleet.org, 03 August 2019
- ^ Low hCG Levels in Pregnancy: What Does It Mean? Medicalnewstoday.com, 03 August 2019
- ^ Hook Effect: Pregnancy Test False-Negative Causes and Meaning Healthline.com, 03 August 2019
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