Urine pregnancy test negative but blood test positive

Why would my HCG test negative but my HP test positive?

I only had a period for 2 days. I’ve had an ectopic pregnancy before. Now I have my period again, but it’s brown instead of red. What’s going on?

Could be a false positive. Home kits have to be used properly and in the right conditions, else it may lead to incorrect results. They also have to be non-contaminated and handled correctly. Brown periods may be worrisome if they are massive. Make sure the brown color isn’t due to something else (feces, foreign body, old clotted blood, etc.)

Stat Pregnancy Test . . . Without Urine?

A 25-year-old woman presents to the emergency department having syncopized in the waiting room, where she was triaged with the chief complaint of abdominal pain. Ectopic pregnancy immediately bubbles to the top of your differential diagnosis.

A 25-year-old woman presents to the emergency department having syncopized in the waiting room, where she was triaged with the chief complaint of abdominal pain. Ectopic pregnancy immediately bubbles to the top of your differential diagnosis.

The patient is too dizzy to walk to the bathroom to give you a urine specimen to check a urine pregnancy test. Plus, she admits that she just urinated in the waiting room bathroom a few minutes ago – so no urine now.

Apply several drops of whole blood (instead of urine) into the pregnancy test cassette. In the photo, the patient was pregnant with a serum beta-HCG level of 250 mIU/mL whose urine and whole blood qualitative tests were both positive.

Did you know that most urine pregnancy test kits are approved for both urine and serum samples? A quick Google search reveals that Accutest, Cardinal Health, ICON, OSOM, and Rapid Response all are approved for both. The question is whether this will work for whole blood. Recall that serum is the extracellular component of whole blood.

One study in the Journal of Emergency Medicine by Dr. Fromm from Maimonides Medical Center looked at exactly this issue(1). Whole blood pregnancy test performed extremely well, especially if positive:

  • Sensitivity 95.8%
  • Specificity 100%
  • Negative predictive value 97.9%
  • Positive predictive value 100%

In their study, very low beta-HCG values (<159 mIU/mL) occasionally yielded a false negative for whole blood pregnancy tests. The whole blood testing approach missed a total nine of 425 pregnancies. Interestingly, the urine pregnancy test was also negative in five of those nine and not performed in the other four.

Believe a positive test. Confirm all tests with a urine qualitative test or quantitative serum beta-HCG.


Be sure to wait at least 5 minutes when using whole blood in the kit. It sometimes takes a while.

Do not apply additional drops of water or saline to the whole blood sample. This causes unnecessary dilution. Just wait for the blood to osmose across the entire test strip.

1. Fromm C, Likourezos A, Haines L, Khan AN, Williams J, Berezow J. Substituting whole blood for urine in a bedside pregnancy test. J Emerg Med. 2012 Sep;43(3):478-82.

2. Habbousche JP, Walker G. Novel use of a urine pregnancy test using whole blood. Am J Emerg Med. 2011 Sep;29(7):840.e3-4.

more on the web

Content for this column taken from

Michelle Lin, MD

Editor-in-Chief of Academic Life in Emergency Medicine

Methotrexate for Ectopic Pregnancy

ACOG Practice Bulletin No. 94: Medical management of ectopic pregnancy. Obstet Gynecol. 2008;111(6):1479-85.

• 2% of all first-trimester pregnancies and 6% of all pregnancy-related deaths

– Prior tubal, pelvic, or abdominal surgery

– Genital infections leading to pelvic inflammatory disease

– Prior ectopic pregnancy

– In utero exposure to diethylstilbestrol (DES)

– History of infertility

– Use of assisted reproductive technologies (in vitro fertilization)

• Dihydrofolate reductase inhibitor – inhibits DNA synthesis, repair, and cell replication

• Overall success rate for treating ectopic pregnancy = 71-94%

• Success rate of single-dose MTX for B-hCG > 5,000 mIU/mL = 85.7%

Side effects: Abdominal pain, nausea/vomiting, stomatitis

Eligibility criteria for MTX in ectopic pregnancy:

• High clinical suspicion or confirmed ectopic pregnancy,

• Able to comply with close follow-up

• Normal creatinine, liver transaminases, WBC, hematocrit, and platelet counts

Contraindications for MTX in ectopic pregnancy:

• Overt or lab evidence of immunodeficiency

• Alcoholism, alcoholic or chronic liver disease

• Preexisting blood dyscrasias or significant anemia

• Known sensitivity to MTX

• Active pulmonary disease

• Peptic ulcer disease

• Hepatic, renal, or hematologic dysfunction

• Gestational sac > 3.5 cm on U/S (relative contraindication)

• Embryonic cardiac motion on U/S (relative contraindication)

• MTX 50 mg/m2 IM on Day 1

• Measure B-hCG on Days 4 and 7

• Check for 15% B-hCG decrease between days 4 and 7

• Measure B-hCG weekly until nonpregnant level

• If B-hCG dose not decrease by >15% as expected, re-dose 50 mg/m2 IM and repeat B-hCG on days 4 and 7 after 2nd dose.

Alternative regimens: Two-Dose and Fixed Multidose regimen

(consider for BhCG level > 5,000 mIU/mL)

>>from the comment stream

Great idea. Could have used this a few years ago when an 18 year old female patient presented unresponsive with a positive FAST exam and hypotensive – we got a urine after cath but, this would have been easier to just use blood sample. She did fine but still less pucker time!

… We’re trying to implement Whole-Blood HCG testing as a Department, and are running into the not “FDA-Approved” barrier. Has anybody else discussed with Lab/Pathology departments about this?

-Daniel Lakoff, MD

I have not implemented formally. I am using only in very time-sensitive, active scenarios (hypotensive young woman whose chief complaint is abdominal pain and vag bleeding). We also get a standard urine pregnancy test or serum beta-hcg as a confirmatory test.

-Michelle Lin, MD

Response letter from Dr. Christian Fromm, first author of the cited study, Substituting Whole Blood for Urine in a Bedside Pregnancy Test

To date we have not formalized a process through our laboratory department. Similar to your shop, we use whole blood to make time-sensitive clinical decisions and then try to confirm. But in light of all the recent interest – I have received several inquiries about this matter – I am considering taking this the next step, and I will keep you abreast of any developments.

I should like to add some detail to your discussion of the cases in which there were discrepancies between the urine or whole blood POC tests and the quantitative serum hCG testing. You correctly point out that the whole blood testing missed 9 out of 425 pregnancies and that the urine test was also negative in 5 of those (those 5 hCGs were 5, 16, 18, 47, and 50). Keep in mind that the test is intended to be 100% sensitive only for hCG >25, so that probably explains the false negatives for 3 of them, but is somewhat troubling that both the urine and whole blood missed the hCGs of 47 and 50.

On that point, we do know that false negative urine pregnancy testing can occur in the presence of high levels of hCG variants [please refer to the very interesting recent article by Dr. Richard T. Griffey: “Hook-Like Effect” Causes False-negative Point-of-Care Urine Pregnancy testing in Emergency Patients. J Emerg Med 2013;44(1)155-160], but I’m not sure how likely that is to be the case here with such low hCG values.

As you point out, the urine test was simply not performed due to oversight in 4 of the other discrepant cases in which the whole blood tests were falsely negative, so we will never know if the urine would have missed those too, but I suspect the urine would not have picked those up either because of the low hCG values, which were 6, 9, 12 and 22 (all below the test’s threshold of 25).

There were no discrepant cases in which the whole blood test was negative but the urine test was positive. However, there were two discrepant cases in which the urine tested negative but the whole blood was positive (those hCGs were 83 and 159). So, according to our data, there is a suggestion that the whole blood may actually be more sensitive than urine, but that might require a larger sampling to establish.

False Positive Pregnancy Test Result and Phantom HCG

A pregnancy hcg test checks for the presence of the pregnancy hormone hCG or human chorionic gonadotropin in your body. A false positive hCG pregnancy test, a positive hCG test when you are not pregnant, rarely happens, but if it happens then it can be seen both with blood and urine tests, though in each case, the causes can be slightly different.

False positive versus false negative pregnancy test

  • A false positive pregnancy test means that your pregnancy test is positive but you are NOT pregnant.
  • A false negative pregnancy testmeans that you test negative but you ARE pregnant.
  • A true positive pregnancy test means that your pregnancy test is positive and you are pregnant.
  • A true negative pregnancy test means that your pregnancy test is negative and you are NOT pregnant.

Most women who have a positive pregnancy test are pregnant and only a few are not. One cause of a false positive pregnancy test is that you do not read your urine pregnancy test correctly. Pregnancy tests have certain instructions and before you make the diagnosis of a positive pregnancy test make sure that you followed all instructions. Most manufacturers suggest to read their test after 3 minutes and to NOT READ it after 10 minutes. Once you have a negative test after 3-5 minutes THROW OUT the test. Any positive test appearing only well after that time is inaccurate and cannot be considered positive. But a false positive pregnancy test can also happen after an hCG injection like it happened to Kim Kardashian.

The urine pregnancy test checks for the presence of the pregnancy hormone hCG human chorionic gonadotropin. hCG made by the placenta which exists only in pregnancy. A positive test that was done correctly has a 99% reliability that you are pregnant. A positive pregnancy test usually means that you are pregnant. There are only a very few circumstances in which a positive pregnancy test means that you are not pregnant (False Positive Test).

False positive urine tests can also occur under the following circumstances:

  • Fertility treatment: If you receive shots of hCG or gonadotropins (for example, Pregynl, Profasi, Pergonal, APL) for ovulation it’s posible to have a positive urine or blood pregnancy test for two to three weeks after the shot and not be pregnant. A rising blood hCG level usually indicates a pregnancy. This is what happened to Kim Kardashian.
  • Evaporation line. If you read the test after the suggested time has passed.
  • Improper Testing – When taking a home pregnancy test, it is very important to read the directions before testing. Your home pregnancy test instructions will specify when test results should be interpreted and when test results are no longer valid. Some tests will produce a faint positive test result if read after the instructed time. You should use a clock or a watch and record the time you perform the test and read results at the instructed time. Guessing how long it has been since performing the test can lead to false results. Three minutes can seem like twenty minutes and vice versa when you are anxiously waiting to find out if you are expecting.
  • Chemical pregnancy – This is a pregnancy that has a positive pregnancy test but the embryo or fetus do not develop
  • Very early pregnancy loss or miscarriage
  • Certain rare medical conditions such as gestational trophoblastic disease, pancreas islet-cell tumors, adenomyosis, gonadoblastoma, bladder cancer, lung cancer, after blood tranfusion.
  • Medications – Some drugs like Methadone, chlordiazepoxide, or promethazine can give a false positive pregnancy test
  • Phantom-hCG” The most important though very rare false positive blood test is a woman who has a low positive blood pregnancy test, the urine test is negative, and she is not pregnant.
  • Menopause: Some women age 50 and older in menopause may have a slightly elevated blood hCG test, which usually is not associated with a pregnancy.
  • Defective Pregnancy Test – Expired tests or faulty home pregnancy tests can also lead to false positive results. Always check the expiration date before testing to assure accurate results. Keep in mind, even with the highest quality control, an occasional defective test may occur.

    If you have tested positive and are unsure about the results of your home pregnancy test, consult your doctor.

    What Is A Phantom hCG And What Causes the False Positive Pregnancy Test

    A “Phantom hCG” is a positive blood pregnancy test without being pregnant. Patients with a phantom hCG will have a persistently and not significantly rising positive blood pregnancy test but the urine test is negative.

    Phantom hCG and phantom choriocarcinoma syndrome (pseudohypergonadotropinemia) refer to persistent mild elevations of hCG, leading physicians to treat patients with cytotoxic chemotherapy for choriocarcinoma when in reality no true hCG or trophoblast disease is present.

    The hCG test, or pregnancy test, is one of the most common tests done in laboratories. It is assumed that an hCG assay detects only hCG or hCGß. This is not always the case. hCG kits can detect a wide and varying range of different hCG-related molecules in serum or urine samples.

    • hCG dissociation and degradation products, like the free ß-subunit, nicked hCG and
    • ß-subunit core fragment
    • hyperglycosylated hCG a variant of hCG with separate biological functions and
    • a pituitary gland-produced variant of hCG

    The reason for a phantom hCG is that some individuals react falsely positive to some substrate in the blood hCG test and thus they will display a consistently low positive blood pregnancy test even though they are not pregnant, but their urine test will be negative. This phantom hCG may lead to serious misdiagnosis and intervention, but can be detected with serial dilutions. Patients with phantom hCG have a positive blood hCG but a negative urine hCG test. Therefore, if there is a question, a urine test should be done together with the blood hCG test.

    Positive Pregnancy Test: When and How Long After Implantation

    A pregnancy test can show a positive result a few days after implantation has occurred. Most women who want to get pregnant are very keen to take a home pregnancy test (HPT) to see if the result is positive. Depending on your body and the levels of hCG hormone, early pregnancy can be detected by a pregnancy blood test as soon as 3-4 days after implantation. Usually, a urine home pregnancy test takes a few days longer to detect a pregnancy and may show a positive result as soon as 5-7 days after implantation.

    Even if the home pregnancy test result is negative, it doesn’t necessarily mean that you are not pregnant. How soon an early pregnancy can be detected depends on the levels of the hormone called human chorionic gonadotropin (hCG). This hormone is produced during pregnancy. Blood and urine pregnancy tests check for elevated levels of hCG which start to rise right after implantation. A positive urine home pregnancy test will undoubtedly mean that you are pregnant and should visit your doctor for hCG blood test.

    Most home urine pregnancy test kits advise that you should wait until the first day of your missed period before taking the test. This is when levels of hCG will usually be high enough for the majority of pregnancy testing kits to show a positive pregnancy result if you have conceived. However, some urine pregnancy testing kits are more sensitive and may be able to show a positive result and detect early pregnancy quite soon after implantation.

    If you have already waited for a few days after your missed period to take a pregnancy test, and it is still negative, chances are that you are not pregnant.

    You may want to take a pregnancy test, but you probably have questions such as: How long after implantation can I test? How long do I have to wait after a missed period before I take a test? In this article, you will find out how early you can detect pregnancy using at-home pregnancy testing kits. You will also learn about the other early signs of pregnancy that can help determine if implantation has taken place.

    How Long After Implantation You Need to Take a Pregnancy Test

    How early you can take a pregnancy test depends on a number of factors such as the sensitivity of the home pregnancy test (HPT), levels of human chorionic gonadotropin (hCG) in your body, and the regularity of your menstrual cycle.

    A pregnancy test can only become positive when an egg is fertilized after ovulation. According to the American Pregnancy Association, ovulation happens about 11 to 21 days from the start of your last period. 1 At ovulation, an egg is released and lives for up to 24 hours in the fallopian tubes waiting for a sperm that lives long enough to fertilize it. Some signs of ovulation include discharge, light abdominal cramping, and some ovulation spotting.

    When the fertilized egg attaches itself to the wall of your uterus, implantation occurs. As soon as implantation happens, your body produces hCG and the pregnancy hormone can be detected in a pregnancy test. At the same time, you may have other signs of implantation such as light spotting that lasts a day or two, mild cramping, tender breasts, and an increased need to pee.

    The length of time after implantation you need to take a pregnancy test to check if it’s positive or not depends on the sensitivity of the pregnancy test that is carried out. The two types of pregnancy tests to check for early pregnancy are:

    • Urine hCG pregnancy test kits that you use at home and show up a mark to indicate a positive pregnancy test or a negative test result.
    • Pregnancy blood tests at the doctor’s office to check for hCG in blood serum in order to detect a pregnancy.

    Urine hCG test – when is it positive after implantation?

    Some of the most sensitive urine pregnancy test kits can detect early pregnancy in less than a week after implantation. The European Society of Human Reproduction and Embryology, found that urine pregnancy testing kits will usually show a positive result 3-4 days after implantation. By 7 days (the time of the expected period) 98% of pregnancy testing kits will be positive. 13

    Urine pregnancy test kits have an hCG sensitivity of 25 mlU/ml (sensitivity of 25 units per litre). The American Pregnancy Association say that a reading of more than 25 mIU/ml in urine indicates pregnancy. 2

    The levels of hCG are detectable a few days after implantation. For example, a report published in a German medical journal said that sensitive pregnancy testing kits can detect hCG as early as 4 days or even 10 days before your next period is due. 3

    According to Dr. Nivin Todd on WebMD, implantation occurs 3-4 days after the egg is fertilized. This may result in implantation bleeding which can be one of the earliest signs of pregnancy. Dr. Todd says that hCG levels will show up in most urine tests from as early as 7 days before you expect your next period. 4

    Sometimes, urine home pregnancy tests show up “false-negative” results because not enough hCG hormone has been detected yet. This means that you could still be pregnant even though the pregnancy test shows up as negative. However, in a few days, the pregnancy test will become positive in women if implantation has taken place.

    You can test for pregnancy using a urine pregnancy test as early as a week before your next period is expected. Even if the results are negative, you shouldn’t lose hope. Take another urine pregnancy test after 5-7 days to see if it becomes positive. According to Lab Tests Online, if you are pregnant, an early positive urine pregnancy test will be reliable 10 days after your missed menstrual period. 5

    Blood hCG Level and early pregnancy test

    A pregnancy blood test will be positive 2 or 3 days before a urine pregnancy test. Pregnancy blood tests check the levels of the hCG hormone and they are more accurate than urine pregnancy tests as they can show the exact levels of hCG.

    Doctors also use hCG levels to determine how many weeks you are pregnant and to monitor your health during pregnancy.

    A blood pregnancy test will become positive very soon after implantation. According to Dr. Melissa Conrad Stöppler on MedicineNet, positive pregnancy blood test result can show up as early as one week after conception. Because implantation happens 3-4 after conception, you might get early pregnancy blood test results that are usually positive within 3 or 4 days after implantation. 6

    In very rare circumstances, you might have a “false-positive” pregnancy test result. Dr. Stöppler says that medication, tumors, or other conditions can show up as a positive pregnancy test when there is, in fact, no pregnancy.

    Pregnancy Test Soon After Implantation – How Accurate Is It?

    A positive pregnancy test is almost certainly correct and is usually very accurate. However, you always need to follow the instructions of the home pregnancy test correctly.

    Doctors from the National Health Service say that if the pregnancy test results are positive, then you are probably pregnant. However, a negative test result is less accurate and isn’t necessarily an indicator that you’re not pregnant. Sometimes, taking the pregnancy test too soon after implantation doesn’t allow for high enough levels of hCG hormone to develop. 7

    Pregnancy tests can show a positive result when the concentration of the pregnancy hormone (hCG) is high enough to be detected in a blood test or urine sample.

    According to Dr. Traci Johnson on WebMD, there are 6 factors that can affect how accurate a pregnancy test is soon after implantation. Some of these are: 8

  • When the urine test was taken. It is usually recommended to take the test first thing in the morning. This is because the concentration of hCG will be higher and makes a positive pregnancy result more likely.
  • When you ovulate. Each woman’s menstrual cycle is different and ovulation may not always happen exactly when planned. Although the average time of ovulation is mid-cycle, your body can release an egg as soon as day 11 of your cycle and as late as day 21.
  • When implantation happens. It can be difficult to know exactly when implantation happens. A fertilized egg takes between 6 to 12 days after ovulation to implant itself in the uterine lining. 1
  • How soon after implantation you take the test. There needs to be enough concentration of hCG for a positive pregnancy test result. It may take time for pregnancy test results to become positive if you have successfully conceived.
  • The sensitivity of the pregnancy test. Doctors from the Mayo Clinic say that some pregnancy testing kits are more sensitive than others. Therefore, some may require a higher amount of pregnancy hormone hCG to show a positive pregnancy test result. 9
  • Blood and urine hCG levels. There are also various factors that can affect pregnancy hormone levels. For example, if you drink too much fluids, you might not get a positive pregnancy reading when taking a urine test soon after implantation.
  • The European Journal of Epidemiology says that smoking and being overweight can also negatively affect hCG levels. This makes it harder to test for early signs of pregnancy soon after implantation. 10

    However, if you are pregnant, then pregnancy test result is usually positive within 7-10 days after you have missed a period.

    How to Test for Pregnancy Soon After Implantation

    Most women use at-home urine pregnancy test kits because they are cheaper and quicker than making an appointment with your doctor for a pregnancy blood test. These will test positive for pregnancy when hCG levels reaches at least 25 mIU/ml.

    To use a urine pregnancy test soon after implantation to check if it tests positive, this is what you should do:

  • Wash your hands with water and soap.
  • Remove the testing kit from its packaging and sit on the toilet seat.
  • Depending on the type of test, you either need to urinate on the testing stick or into a small plastic cup.
  • The urine sample should be from midstream, so you should pee a little before collecting urine in the cup or placing the stick in the urine stream.
  • If you are using the urine collection method to test for pregnancy, follow the instructions on using the dropper.
  • Now, it’s time to wait. The best thing is to do something to distract yourself for the 5 minutes or so it takes the test to show positive or negative.
  • Check the results.
  • What do Pregnancy Test Results Mean After Implantation?

    Positive pregnancy results usually mean that you are pregnant. Most home pregnancy testing kits show the results by means of a line to indicate a positive or a negative result. Dr. Traci Johnson on WebMD says that even if the line for a positive pregnancy test result is very faint, it still means you are pregnant. 8

    If your pregnancy test is positive, then it means that you should make an appointment to see your doctor. The earlier you can arrange for prenatal care, then the better health you and your baby will enjoy during pregnancy.

    Negative pregnancy results may not necessarily mean that implantation hasn’t happened. You could still be pregnant because you tested too soon after implantation or you took the test the wrong way. Dr. Traci Johnson recommends retesting for a positive result in a week to check for pregnancy.

    If the HPT still tests negative over 10 days after your missed period, you should speak to your doctor. A late or missed period could be a result of a hormonal imbalance as well as emotional stress, excessive weight loss or gain and problems with pelvic organs. 12

    Early Signs of Pregnancy Very Soon After Implantation

    Even before an hCG pregnancy test becomes positive, you may have some signs of implantation that show up before a pregnancy test confirms that you are pregnant.

    Implantation spotting. Many women experience implantation spotting as one of the earliest pregnancy signs. Implantation bleeding looks like very light spotting that could be a rusty brown or light pink color. Spotting associated with implantation usually last up to 2 days.

    Implantation cramping. Around the time when the fertilized egg attaches to the uterine lining you might experience mild cramping. Implantation cramping usually happens just before or just after you notice implantation spotting.

    Breast tenderness. Doctors from the American Pregnancy Association say that your breasts may become sore when implantation happens. In fact, your breasts may appear swollen and tender even as early as 1 to 2 weeks after conception. 11

    Other signs of implantation or early pregnancy that you might notice before a pregnancy test tests positive are frequent urination, food aversions or cravings, backaches and headaches, and mood swings.

    If you notice these signs of pregnancy, and you know that you had intercourse around the time of ovulation, you should take a home pregnancy test. If the results are negative, they may become positive several days later as pregnancy hormone (hCG) increases.

    По материалам:


    Stat Pregnancy Test . . . Without Urine?


    Positive Pregnancy Test: When and How Long After Implantation

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