What does the book mean on a pregnancy test

1. HCG Function
2. HCG is a glycoprotein Hormone with subunits a and b
   1. Composed of 65% polypeptides by molecular weight
   2. Composed of 35% large sugar side chains (8 chains)
      1. Four are N-Linked (2 each on alpha and beta)
      2. Four are O-Linked (all 4 are on beta subunit)
   3. Forms of HCG found in blood and urine
      1. Intact HCG with alpha and beta subunits
      2. Nicked HCG and nicked free beta subunit
      3. Free Beta hCG subunit and free alpha HCG subunit
      4. Hyperglycosylated free beta and free alpha subunits
      5. Beta core fragment (present only in urine)
3. HCG shares the same alpha subunit with other Hormones
   1. Luteinizing Hormone (LH)
   2. Thyroid Stimulating Hormone (TSH)
4. Urine and Blood HCG tests are specific for beta subunit
5. Serum half life of HCG: 24 to 36 hours
6. Discriminatory values at which bHCG is positive
   1. Urine bHCG: 20-25 IU/ml
   2. Serum bHCG: 10 IU/ml

• Interpretation
• Levels of bHCG in pregnancy

1. Estimation in pregnancy for weeks 4 to 8 (plateaus after 10 weeks)
2. Chart of corresponding Gestational age
   1. Day 23 (3.3 weeks): 100 mIU/ml (correlates with blastocyst implantation)
   2. Day 28 (4.0 weeks): 250 mIU/ml (approximate time of first missed Menses)
   3. Day 35 (5.0 weeks): 1000 mIU/ml
   4. Day 42 (6.0 weeks): 4000 mIU/ml
   5. Day 49 (7.0 weeks): 15000 mIU/ml
      1. bHCG 20,000: 5-10 mm Embryo with cardiac activity
   6. Day 56 (8.0 weeks): 65000 mIU/ml
   7. Decreases gradually after 8 weeks
   8. Plateaus after 20 weeks
3. Ranges of bHCG over each Trimester
   1. First Trimester: 30,000 to 100,000 mIU/ml
   2. Second Trimester: 10,000 to 30,000 mIU/ml
   3. Third Trimester: 5,000 to 15,000 mIU/ml

• Causes
• Elevated bHCG in Non-Pregnant State

• Causes
• False Positive increased serum hCG

1. Causes
2. Confirmation methods in non-pregnant conditions
   1. Qualitative urine hCG
   2. Serum hCG by different immunoassay method
   3. Serial dilutions of serum hCG sample

• Causes
• False Negative bHCG

1. Dilute urine
2. High Vitamin C intake

• Interpretation
• HCG in Nonseminomatous germ cell tumor (Men)

1. Interpretation
   1. Poor prognosis if bHCG >50,000 mIU/ml at diagnosis
   2. Five year survival rate: 50%
2. Efficacy
3. Protocol
   1. Initial: bHCG with AFP q1-2 months for 1 year
   2. Later: bHCG with AFP q3 months for 1 year

When you take a pregnancy test your biggest concern is likely the accuracy of the result. Many people share this worry and it can linger even after they get an answer. While pregnancy tests are generally accurate, they can produce errors.

There are several mistakes people make when they take a home pregnancy test that can lead to an inaccurate result. There are two categories of errors when taking a home pregnancy test: those related to timing and those related to interpretation.

• Timing. You took the test too early, didn't wait long enough to read the results, or waited too long to read the results.
• Interpretation. You didn't believe a positive test result (false positive pregnancy tests are unlikely) or you didn't confirm a negative test (which can involve retesting later).

Deciding when to take a home pregnancy test used to be simple: you waited until the day you missed your period and then you took a test. Today, you can get a pregnancy test that claims to tell you if you're pregnant before you've missed your period.

While these tests can produce an accurate result, it depends on the person. Not every person who is pregnant will have the same levels of hCG in their urine. This error isn't inherent to the test, but rather, the timing of taking the test.

Most home pregnancy tests have explicit directions for taking the test and reading the results. The tests will usually give you the exact timeframe in which to look at the test to get your result.

As the urine travels through the indicator window it might look like both lines are present, or that a plus sign is present. However, this does not mean that you are pregnant—it simply means that the test is working.

You must wait until the end of the time allotted in the instructions to read the results of your test—which is usually one or two minutes. Use a stopwatch or a timer app on your phone to keep track.

While you don't want to read the results of your pregnancy test too early, you also don't want to way too long. If you take a test when you wake up, then hop right in the shower, you might get on with your day without checking the test again.

The instructions will usually give you the window in which the test results will be accurate—usually about five minutes. After this time has gone by, the test might produce a faint positive when in fact there was no hCG detected in your urine.

If you've read the results within the timeframe in the instructions and decide to keep the test, don't read into any change in the result in the hours or days after you take it.

There are very few instances where a positive pregnancy test is wrong. A false positive pregnancy test is more likely to be caused by user error rather than a problem with the test. A negative result, on the other hand, may happen if you took a test too soon.

If you are not pregnant, a false positive pregnancy test result is unlikely. The more likely explanation is that you had a chemical pregnancy (which produces enough hCG to turn a pregnancy test positive but miscarries shortly after) or a very early miscarriage.

If you get a positive pregnancy test, assume that you are pregnant (which includes making an appointment with your health care provider to have the result confirmed).

There are some situations where you would want to take another pregnancy test after getting a negative result. If the negative result was unexpected or you still do not have your period within a week of taking the test, you will want to retest.

Sometimes, a negative test might not truly be a negative test—it might just be early for the test to turn positive. This is why most pregnancy tests recommend retesting after your body has had more time to produce detectable amounts of hCG in your urine.

There are several reasons that home pregnancy tests can produce inaccurate results. The good news is, these errors can be avoided if you follow the instructions carefully. While most errors are related to user mistakes and not a problem with the test itself, purchasing a quality test makes it less likely it will have defects or be expired.

If you get a test result that is unexpected, follow the recommendations provided by the test for retaking it (usually within a week). It's also important that you contact your health care provider to confirm the result you get with a home pregnancy test.

Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

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2. Johnson S, Cushion M, Bond S, Godbert S, Pike J. Comparison of analytical sensitivity and women's interpretation of home pregnancy tests. Clin Chem Lab Med. 2015;53(3):391-402. doi:10.1515/cclm-2014-0643

• ACOG Committee Opinion No. 278, November 2002 (reaffirmed 2020). Avoiding inappropriate clinical decisions based on false-positve human chorionic gonadotropin test results. Int J Gynaecol Obstet. 2003;80(2):231-233. doi:10.1016/s0020-7292(03)00021-3

• Er TK, Chiang C-H, Cheng BH, Hong FJ, Lee CP, Ginés MÁR. False-positive urine pregnancy test in a woman with adenomysosis. Am J Emerg Med. 2009;27(8):1019.e5-1019.e7. doi:10.1016/j.ajem.2008.12.023